- published: 05 Jun 2016
- views: 149055
Create your page here
Flow separation
All solid objects traveling through a fluid (or alternatively a stationary object exposed to a moving fluid) acquire a boundary layer of fluid around them where viscous forces occur in the layer of fluid close to the solid surface. Boundary layers can be either laminar or turbulent. A reasonable assessment of whether the boundary layer will be laminar or turbulent can be made by calculating the Reynolds number of the local flow conditions.
Flow separation occurs when the boundary layer travels far enough against an adverse pressure gradient that the speed of the boundary layer relative to the object falls almost to zero. The fluid flow becomes detached from the surface of the object, and instead takes the forms of eddies and vortices. In aerodynamics, flow separation can often result in increased drag, particularly pressure drag which is caused by the pressure differential between the front and rear surfaces of the object as it travels through the fluid. For this reason much effort and research has gone into the design of aerodynamic and hydrodynamic surfaces which delay flow separation and keep the local flow attached for as long as possible. Examples of this include the fur on a tennis ball, dimples on a golf ball, turbulators on a glider, which induce an early transition to turbulent flow regime; vortex generators on light aircraft, for controlling the separation pattern; and leading edge extensions for high angles of attack on the wings of aircraft such as the F/A-18 Hornet.
This page contains text from Wikipedia, the Free Encyclopedia - https://wn.com/Flow_separation
Podcasts:
-
What Causes Stall/Flow Separation? Adverse Pressure Gradient Explained
How does Stall/Flow Separation work? The adverse pressure gradient is the dominant mechanism behind flow separation from aerodynamic bodies and stall on wings. An adverse pressure gradient exists whenever a flow travels from a region of low pressure to a region of high pressure. If it is strong enough, it can reverse the direction of the boundary layer, causing flow recirculation and separation. Facebook: https://www.facebook.com/Kyleengineers Patreon: https://www.patreon.com/KYLEDRIVES Instagram: https://www.instagram.com/shadowraceengineering/ Race car consulting: http://www.jkfaero.com G+: https://plus.google.com/103663408131824188800 Youtube: https://www.youtube.com/user/Kyleengineers
published: 05 Jun 2016 -
Flow Separation - Boundary layer separation explained
For more information, visit https://www.airshaper.com or email [email protected] ---------------------------------------------------------------------------------------- In this video we’ll explain flow separation (or boundary layer separation). In our previous video on boundary layers, we saw that the air close to the surface will stick to it, forming a boundary layer. But in some cases, it can become too difficult for the air to follow the curvature of the surface, causing it to detach. Let’s have a look at why this can happen. When you look at air flowing across a flat plate, as in our previous video, the free stream velocity remains constant. Because of Bernoulli’s equation, which states that pressure changes with velocity, this means the pressure gradient in the X-direction is more...
published: 21 Sep 2021 -
Boundary layer separation and stall
published: 07 Jan 2015 -
Flow separation
From "Fundamental Principles of Flows" and "Form Drag, Lift, and Propulsion" - (Hunter Rouse) Courtesy of Dr Marian Muste, IIHR - Hydroscience & Engineering, University of Iowa. The Fluids Laboratory is an integrated learning environment developed by IIHR-Hydroscience & Engineering for the College of Engineering of The University of Iowa. http://www.iahrmedialibrary.net/
published: 26 Nov 2013 -
GATE 2019 | Fluid Mechanics | Flow Separation / Boundary Layer Separation
If you are preparing or want to prepare for GATE 2019, then you have come to the right place 👍🏻 I regularly upload concised quality videos, specifically designed for Mechanical and Civil Engineering GATE Exam. I even solve the important questions of previous years GATE Exam. If you find my channel useful then please SUBSCRIBE it 🙏🏻 🙂 And do not forget to click the BELL 🛎 icon 🙂 #flowseparation #fluidmechanics #gatemechanical #gate2019 #gatecivil You even can ask any doubt related to GATE exam to #drgate, I will do my best to help you 🙂
published: 26 Aug 2018 -
What is a Boundary Layer? | Cause of Boundary Layer Formation | Types and Impact of Boundary Layers
Hi. In this video we look at what is a boundary layer and what causes a boundary layer to form on the surface of an object moving across a viscous fluid. We look at the changes that happen because of the boundary layer and the 2 types of boundary layers: Laminar and Turbulent. We see the impact of the Boundary layer formation on different surfaces and how a turbulent boundary layer is still useful for a few applications. hope its useful!! Got Feedback! Mail it to [email protected] Thank You! Please Watch and Subscribe!
published: 02 Mar 2022 -
Flow Separation and Reattachment — Lesson 4
This video lesson starts by describing how the velocity of the fluid in the boundary layer at the surface of the object is equal to the object’s velocity. When the fluid flows around an object, an adverse pressure layer forms that separates the boundary layer from the surface. Under certain circumstances a separated flow can become reattached to the surface again. This lesson is part of the Ansys Innovation Course: Real External Flows. To access this and all of our free, online courses — featuring additional videos, quizzes and handouts — visit Ansys Innovation Courses at https://www.ansys.com/courses.
published: 24 Nov 2020 -
Understanding Aerodynamic Drag
Get access to the extended version of this and other videos (without any ads) on Nebula - https://nebula.tv/videos/the-efficient-engineer-understanding-aerodynamic-drag-extended-version Drag and lift are the forces which act on a body moving through a fluid, or on a stationary object in a flowing fluid. We call these aerodynamic forces (if the fluid is a gas) or hydrodynamic forces (if the fluid is a liquid). This video is all about the drag force. There are two main causes of drag - first we have the pressure distribution around the object, which is particularly significant if flow separation occurs. And then we have the shear stresses acting on the object, which are most significant for streamlined bodies. --- Follow me on Twitter: https://twitter.com/efficiengineer If you would lik...
published: 12 Jan 2021 -
Aside: Boundary Layer Separation
This clip explains why boundary layers separate and compares boundary layers with the Couette and Poiseuille flow studied in chapter 3. It then explains some of the consequences for flow around wings and other objects.
published: 27 May 2015 -
Separation of Boundary layer
published: 27 Feb 2018
developed with YouTube
5:37
What Causes Stall/Flow Separation? Adverse Pressure Gradient Explained
- Order: Reorder
- Duration: 5:37
- Uploaded Date: 05 Jun 2016
- views: 149055
How does Stall/Flow Separation work? The adverse pressure gradient is the dominant mechanism behind flow separation from aerodynamic bodies and stall on wings. ...
How does Stall/Flow Separation work? The adverse pressure gradient is the dominant mechanism behind flow separation from aerodynamic bodies and stall on wings. An adverse pressure gradient exists whenever a flow travels from a region of low pressure to a region of high pressure. If it is strong enough, it can reverse the direction of the boundary layer, causing flow recirculation and separation.
Facebook: https://www.facebook.com/Kyleengineers
Patreon: https://www.patreon.com/KYLEDRIVES
Instagram: https://www.instagram.com/shadowraceengineering/
Race car consulting: http://www.jkfaero.com
G+: https://plus.google.com/103663408131824188800
Youtube: https://www.youtube.com/user/Kyleengineers
https://wn.com/What_Causes_Stall_Flow_Separation_Adverse_Pressure_Gradient_Explained
How does Stall/Flow Separation work? The adverse pressure gradient is the dominant mechanism behind flow separation from aerodynamic bodies and stall on wings. An adverse pressure gradient exists whenever a flow travels from a region of low pressure to a region of high pressure. If it is strong enough, it can reverse the direction of the boundary layer, causing flow recirculation and separation.
Facebook: https://www.facebook.com/Kyleengineers
Patreon: https://www.patreon.com/KYLEDRIVES
Instagram: https://www.instagram.com/shadowraceengineering/
Race car consulting: http://www.jkfaero.com
G+: https://plus.google.com/103663408131824188800
Youtube: https://www.youtube.com/user/Kyleengineers
4:08
Flow Separation - Boundary layer separation explained
- Order: Reorder
- Duration: 4:08
- Uploaded Date: 21 Sep 2021
- views: 55766
For more information, visit https://www.airshaper.com or email [email protected]
------------------------------------------------------------------------------...
For more information, visit https://www.airshaper.com or email [email protected]
----------------------------------------------------------------------------------------
In this video we’ll explain flow separation (or boundary layer separation).
In our previous video on boundary layers, we saw that the air close to the surface will stick to it, forming a boundary layer. But in some cases, it can become too difficult for the air to follow the curvature of the surface, causing it to detach. Let’s have a look at why this can happen.
When you look at air flowing across a flat plate, as in our previous video, the free stream velocity remains constant. Because of Bernoulli’s equation, which states that pressure changes with velocity, this means the pressure gradient in the X-direction is more or less to zero. Also, the pressure is imposed onto the boundary layer and so doesn’t really change much in the direction perpendicular to the surface either. That means the pressure gradient in both the x and y direction are close to zero.
But when the air flows around a curved surface, it speeds up and slows down. Take the flow around a cylinder for example: at the front, the pressure is the highest as the air comes to a complete standstill – this is the stagnation point. As the air then curves around the cylinder, it speeds up and this creates a drop in pressure. As the pressure goes down with increasing x, this is a negative pressure gradient, which is good: the air is being pushed downstream, overcoming the friction in the boundary layer, which gradually builds up.
The maximum velocity is reached somewhere around the midpoint of the cylinder, after which the air starts to slow down again. This means the pressure gradient is now reversed: as the air travels across the surface, the pressure goes up. This is what is called an “adverse” pressure gradient and the air is no longer driven but obstructed by the pressure difference: it has to flow into regions with higher pressure.
If the pressure gradient is positive or zero, as in the case of the flat plate, then the velocity gradient perpendicular to the wall is positive: the further you move away from the wall, the higher the velocity. But when the air travels against an adverse pressure gradient, the velocity profile is pushed back and this reduces the velocity gradient at the wall.
At some point, the velocity gradient becomes zero, which is the point where the flow separates or detaches. Beyond this point, the velocity profile is zero both at the wall, because of the no-slip condition, and at the inflection point, which is where the velocity crosses from negative into positive. In the negative velocity region, between the surface and the inflection point, the air flows in a direction opposite to the main flow – this is called a recirculation. The separated flow will now surf on top of this recirculation flow and the boundary layer and wake will continue to grow, which can have a negative effect on drag.
In reality, shapes can be much more complex than cylinders and flows can detach and reattach in various locations. Even on a smooth wing, the flow can detach and reattach. So, this is very much a 3-dimensional challenge and getting it right requires a careful analysis and optimization of local and global pressure gradients.
Also, keep in mind that flow separation can happen in both laminar and turbulent boundary layers. Turbulent boundary layers, however, carry more momentum and will typically stay attached to the surface further downstream compared to a laminar one – just check our video on golf ball dimples or vortex generators to learn more.
https://wn.com/Flow_Separation_Boundary_Layer_Separation_Explained
For more information, visit https://www.airshaper.com or email [email protected]
----------------------------------------------------------------------------------------
In this video we’ll explain flow separation (or boundary layer separation).
In our previous video on boundary layers, we saw that the air close to the surface will stick to it, forming a boundary layer. But in some cases, it can become too difficult for the air to follow the curvature of the surface, causing it to detach. Let’s have a look at why this can happen.
When you look at air flowing across a flat plate, as in our previous video, the free stream velocity remains constant. Because of Bernoulli’s equation, which states that pressure changes with velocity, this means the pressure gradient in the X-direction is more or less to zero. Also, the pressure is imposed onto the boundary layer and so doesn’t really change much in the direction perpendicular to the surface either. That means the pressure gradient in both the x and y direction are close to zero.
But when the air flows around a curved surface, it speeds up and slows down. Take the flow around a cylinder for example: at the front, the pressure is the highest as the air comes to a complete standstill – this is the stagnation point. As the air then curves around the cylinder, it speeds up and this creates a drop in pressure. As the pressure goes down with increasing x, this is a negative pressure gradient, which is good: the air is being pushed downstream, overcoming the friction in the boundary layer, which gradually builds up.
The maximum velocity is reached somewhere around the midpoint of the cylinder, after which the air starts to slow down again. This means the pressure gradient is now reversed: as the air travels across the surface, the pressure goes up. This is what is called an “adverse” pressure gradient and the air is no longer driven but obstructed by the pressure difference: it has to flow into regions with higher pressure.
If the pressure gradient is positive or zero, as in the case of the flat plate, then the velocity gradient perpendicular to the wall is positive: the further you move away from the wall, the higher the velocity. But when the air travels against an adverse pressure gradient, the velocity profile is pushed back and this reduces the velocity gradient at the wall.
At some point, the velocity gradient becomes zero, which is the point where the flow separates or detaches. Beyond this point, the velocity profile is zero both at the wall, because of the no-slip condition, and at the inflection point, which is where the velocity crosses from negative into positive. In the negative velocity region, between the surface and the inflection point, the air flows in a direction opposite to the main flow – this is called a recirculation. The separated flow will now surf on top of this recirculation flow and the boundary layer and wake will continue to grow, which can have a negative effect on drag.
In reality, shapes can be much more complex than cylinders and flows can detach and reattach in various locations. Even on a smooth wing, the flow can detach and reattach. So, this is very much a 3-dimensional challenge and getting it right requires a careful analysis and optimization of local and global pressure gradients.
Also, keep in mind that flow separation can happen in both laminar and turbulent boundary layers. Turbulent boundary layers, however, carry more momentum and will typically stay attached to the surface further downstream compared to a laminar one – just check our video on golf ball dimples or vortex generators to learn more.
- published: 21 Sep 2021
- views: 55766
0:39
Boundary layer separation and stall
- Order: Reorder
- Duration: 0:39
- Uploaded Date: 07 Jan 2015
- views: 160249
- published: 07 Jan 2015
- views: 160249
5:22
Flow separation
- Order: Reorder
- Duration: 5:22
- Uploaded Date: 26 Nov 2013
- views: 48150
From "Fundamental Principles of Flows" and "Form Drag, Lift, and Propulsion" - (Hunter Rouse)
Courtesy of Dr Marian Muste, IIHR - Hydroscience & Engineering, Un...
From "Fundamental Principles of Flows" and "Form Drag, Lift, and Propulsion" - (Hunter Rouse)
Courtesy of Dr Marian Muste, IIHR - Hydroscience & Engineering, University of Iowa.
The Fluids Laboratory is an integrated learning environment developed by IIHR-Hydroscience & Engineering for the College of Engineering of The University of Iowa.
http://www.iahrmedialibrary.net/
https://wn.com/Flow_Separation
From "Fundamental Principles of Flows" and "Form Drag, Lift, and Propulsion" - (Hunter Rouse)
Courtesy of Dr Marian Muste, IIHR - Hydroscience & Engineering, University of Iowa.
The Fluids Laboratory is an integrated learning environment developed by IIHR-Hydroscience & Engineering for the College of Engineering of The University of Iowa.
http://www.iahrmedialibrary.net/
- published: 26 Nov 2013
- views: 48150
8:54
GATE 2019 | Fluid Mechanics | Flow Separation / Boundary Layer Separation
- Order: Reorder
- Duration: 8:54
- Uploaded Date: 26 Aug 2018
- views: 9897
If you are preparing or want to prepare for GATE 2019, then you have come to the right place 👍🏻 I regularly upload concised quality videos, specifically design...
If you are preparing or want to prepare for GATE 2019, then you have come to the right place 👍🏻 I regularly upload concised quality videos, specifically designed for Mechanical and Civil Engineering GATE Exam. I even solve the important questions of previous years GATE Exam. If you find my channel useful then please SUBSCRIBE it 🙏🏻 🙂 And do not forget to click the BELL 🛎 icon 🙂
#flowseparation
#fluidmechanics
#gatemechanical
#gate2019
#gatecivil
You even can ask any doubt related to GATE exam to #drgate, I will do my best to help you 🙂
https://wn.com/Gate_2019_|_Fluid_Mechanics_|_Flow_Separation_Boundary_Layer_Separation
If you are preparing or want to prepare for GATE 2019, then you have come to the right place 👍🏻 I regularly upload concised quality videos, specifically designed for Mechanical and Civil Engineering GATE Exam. I even solve the important questions of previous years GATE Exam. If you find my channel useful then please SUBSCRIBE it 🙏🏻 🙂 And do not forget to click the BELL 🛎 icon 🙂
#flowseparation
#fluidmechanics
#gatemechanical
#gate2019
#gatecivil
You even can ask any doubt related to GATE exam to #drgate, I will do my best to help you 🙂
- published: 26 Aug 2018
- views: 9897
4:17
What is a Boundary Layer? | Cause of Boundary Layer Formation | Types and Impact of Boundary Layers
- Order: Reorder
- Duration: 4:17
- Uploaded Date: 02 Mar 2022
- views: 87965
Hi. In this video we look at what is a boundary layer and what causes a boundary layer to form on the surface of an object moving across a viscous fluid.
We l...
Hi. In this video we look at what is a boundary layer and what causes a boundary layer to form on the surface of an object moving across a viscous fluid.
We look at the changes that happen because of the boundary layer and the 2 types of boundary layers: Laminar and Turbulent. We see the impact of the Boundary layer formation on different surfaces and how a turbulent boundary layer is still useful for a few applications.
hope its useful!!
Got Feedback! Mail it to [email protected]
Thank You! Please Watch and Subscribe!
https://wn.com/What_Is_A_Boundary_Layer_|_Cause_Of_Boundary_Layer_Formation_|_Types_And_Impact_Of_Boundary_Layers
Hi. In this video we look at what is a boundary layer and what causes a boundary layer to form on the surface of an object moving across a viscous fluid.
We look at the changes that happen because of the boundary layer and the 2 types of boundary layers: Laminar and Turbulent. We see the impact of the Boundary layer formation on different surfaces and how a turbulent boundary layer is still useful for a few applications.
hope its useful!!
Got Feedback! Mail it to [email protected]
Thank You! Please Watch and Subscribe!
- published: 02 Mar 2022
- views: 87965
11:32
Flow Separation and Reattachment — Lesson 4
- Order: Reorder
- Duration: 11:32
- Uploaded Date: 24 Nov 2020
- views: 8812
This video lesson starts by describing how the velocity of the fluid in the boundary layer at the surface of the object is equal to the object’s velocity. When ...
This video lesson starts by describing how the velocity of the fluid in the boundary layer at the surface of the object is equal to the object’s velocity. When the fluid flows around an object, an adverse pressure layer forms that separates the boundary layer from the surface. Under certain circumstances a separated flow can become reattached to the surface again. This lesson is part of the Ansys Innovation Course: Real External Flows. To access this and all of our free, online courses — featuring additional videos, quizzes and handouts — visit Ansys Innovation Courses at https://www.ansys.com/courses.
https://wn.com/Flow_Separation_And_Reattachment_—_Lesson_4
This video lesson starts by describing how the velocity of the fluid in the boundary layer at the surface of the object is equal to the object’s velocity. When the fluid flows around an object, an adverse pressure layer forms that separates the boundary layer from the surface. Under certain circumstances a separated flow can become reattached to the surface again. This lesson is part of the Ansys Innovation Course: Real External Flows. To access this and all of our free, online courses — featuring additional videos, quizzes and handouts — visit Ansys Innovation Courses at https://www.ansys.com/courses.
- published: 24 Nov 2020
- views: 8812
16:43
Understanding Aerodynamic Drag
- Order: Reorder
- Duration: 16:43
- Uploaded Date: 12 Jan 2021
- views: 965455
Get access to the extended version of this and other videos (without any ads) on Nebula - https://nebula.tv/videos/the-efficient-engineer-understanding-aerodyna...
Get access to the extended version of this and other videos (without any ads) on Nebula - https://nebula.tv/videos/the-efficient-engineer-understanding-aerodynamic-drag-extended-version
Drag and lift are the forces which act on a body moving through a fluid, or on a stationary object in a flowing fluid. We call these aerodynamic forces (if the fluid is a gas) or hydrodynamic forces (if the fluid is a liquid).
This video is all about the drag force. There are two main causes of drag - first we have the pressure distribution around the object, which is particularly significant if flow separation occurs. And then we have the shear stresses acting on the object, which are most significant for streamlined bodies.
---
Follow me on Twitter: https://twitter.com/efficiengineer
If you would like to support the channel, please consider becoming a Patron - https://www.patreon.com/efficientengineer. This will allow me to create more high quality videos covering a range of engineering topics.
Sound effects by Epidemic Sound: http://epidemicsound.com/creator
---
https://wn.com/Understanding_Aerodynamic_Drag
Get access to the extended version of this and other videos (without any ads) on Nebula - https://nebula.tv/videos/the-efficient-engineer-understanding-aerodynamic-drag-extended-version
Drag and lift are the forces which act on a body moving through a fluid, or on a stationary object in a flowing fluid. We call these aerodynamic forces (if the fluid is a gas) or hydrodynamic forces (if the fluid is a liquid).
This video is all about the drag force. There are two main causes of drag - first we have the pressure distribution around the object, which is particularly significant if flow separation occurs. And then we have the shear stresses acting on the object, which are most significant for streamlined bodies.
---
Follow me on Twitter: https://twitter.com/efficiengineer
If you would like to support the channel, please consider becoming a Patron - https://www.patreon.com/efficientengineer. This will allow me to create more high quality videos covering a range of engineering topics.
Sound effects by Epidemic Sound: http://epidemicsound.com/creator
---
- published: 12 Jan 2021
- views: 965455
15:11
Aside: Boundary Layer Separation
- Order: Reorder
- Duration: 15:11
- Uploaded Date: 27 May 2015
- views: 67931
This clip explains why boundary layers separate and compares boundary layers with the Couette and Poiseuille flow studied in chapter 3. It then explains some of...
This clip explains why boundary layers separate and compares boundary layers with the Couette and Poiseuille flow studied in chapter 3. It then explains some of the consequences for flow around wings and other objects.
https://wn.com/Aside_Boundary_Layer_Separation
This clip explains why boundary layers separate and compares boundary layers with the Couette and Poiseuille flow studied in chapter 3. It then explains some of the consequences for flow around wings and other objects.
- published: 27 May 2015
- views: 67931
0:50
Separation of Boundary layer
- Order: Reorder
- Duration: 0:50
- Uploaded Date: 27 Feb 2018
- views: 741
- published: 27 Feb 2018
- views: 741
5:37
What Causes Stall/Flow Separation? Adverse Pressure Gradient Explained
How does Stall/Flow Separation work? The adverse pressure gradient is the dominant mechani...
published: 05 Jun 2016
What Causes Stall/Flow Separation? Adverse Pressure Gradient Explained
What Causes Stall/Flow Separation? Adverse Pressure Gradient Explained
- Report rights infringement
- published: 05 Jun 2016
- views: 149055
How does Stall/Flow Separation work? The adverse pressure gradient is the dominant mechanism behind flow separation from aerodynamic bodies and stall on wings. An adverse pressure gradient exists whenever a flow travels from a region of low pressure to a region of high pressure. If it is strong enough, it can reverse the direction of the boundary layer, causing flow recirculation and separation.
Facebook: https://www.facebook.com/Kyleengineers
Patreon: https://www.patreon.com/KYLEDRIVES
Instagram: https://www.instagram.com/shadowraceengineering/
Race car consulting: http://www.jkfaero.com
G+: https://plus.google.com/103663408131824188800
Youtube: https://www.youtube.com/user/Kyleengineers
4:08
Flow Separation - Boundary layer separation explained
For more information, visit https://www.airshaper.com or email [email protected]
--------...
published: 21 Sep 2021
Flow Separation - Boundary layer separation explained
Flow Separation - Boundary layer separation explained
- Report rights infringement
- published: 21 Sep 2021
- views: 55766
For more information, visit https://www.airshaper.com or email [email protected]
----------------------------------------------------------------------------------------
In this video we’ll explain flow separation (or boundary layer separation).
In our previous video on boundary layers, we saw that the air close to the surface will stick to it, forming a boundary layer. But in some cases, it can become too difficult for the air to follow the curvature of the surface, causing it to detach. Let’s have a look at why this can happen.
When you look at air flowing across a flat plate, as in our previous video, the free stream velocity remains constant. Because of Bernoulli’s equation, which states that pressure changes with velocity, this means the pressure gradient in the X-direction is more or less to zero. Also, the pressure is imposed onto the boundary layer and so doesn’t really change much in the direction perpendicular to the surface either. That means the pressure gradient in both the x and y direction are close to zero.
But when the air flows around a curved surface, it speeds up and slows down. Take the flow around a cylinder for example: at the front, the pressure is the highest as the air comes to a complete standstill – this is the stagnation point. As the air then curves around the cylinder, it speeds up and this creates a drop in pressure. As the pressure goes down with increasing x, this is a negative pressure gradient, which is good: the air is being pushed downstream, overcoming the friction in the boundary layer, which gradually builds up.
The maximum velocity is reached somewhere around the midpoint of the cylinder, after which the air starts to slow down again. This means the pressure gradient is now reversed: as the air travels across the surface, the pressure goes up. This is what is called an “adverse” pressure gradient and the air is no longer driven but obstructed by the pressure difference: it has to flow into regions with higher pressure.
If the pressure gradient is positive or zero, as in the case of the flat plate, then the velocity gradient perpendicular to the wall is positive: the further you move away from the wall, the higher the velocity. But when the air travels against an adverse pressure gradient, the velocity profile is pushed back and this reduces the velocity gradient at the wall.
At some point, the velocity gradient becomes zero, which is the point where the flow separates or detaches. Beyond this point, the velocity profile is zero both at the wall, because of the no-slip condition, and at the inflection point, which is where the velocity crosses from negative into positive. In the negative velocity region, between the surface and the inflection point, the air flows in a direction opposite to the main flow – this is called a recirculation. The separated flow will now surf on top of this recirculation flow and the boundary layer and wake will continue to grow, which can have a negative effect on drag.
In reality, shapes can be much more complex than cylinders and flows can detach and reattach in various locations. Even on a smooth wing, the flow can detach and reattach. So, this is very much a 3-dimensional challenge and getting it right requires a careful analysis and optimization of local and global pressure gradients.
Also, keep in mind that flow separation can happen in both laminar and turbulent boundary layers. Turbulent boundary layers, however, carry more momentum and will typically stay attached to the surface further downstream compared to a laminar one – just check our video on golf ball dimples or vortex generators to learn more.
0:39
Boundary layer separation and stall
published: 07 Jan 2015
Boundary layer separation and stall
Boundary layer separation and stall
- Report rights infringement
- published: 07 Jan 2015
- views: 160249
5:22
Flow separation
From "Fundamental Principles of Flows" and "Form Drag, Lift, and Propulsion" - (Hunter Rou...
published: 26 Nov 2013
Flow separation
Flow separation
- Report rights infringement
- published: 26 Nov 2013
- views: 48150
From "Fundamental Principles of Flows" and "Form Drag, Lift, and Propulsion" - (Hunter Rouse)
Courtesy of Dr Marian Muste, IIHR - Hydroscience & Engineering, University of Iowa.
The Fluids Laboratory is an integrated learning environment developed by IIHR-Hydroscience & Engineering for the College of Engineering of The University of Iowa.
http://www.iahrmedialibrary.net/
8:54
GATE 2019 | Fluid Mechanics | Flow Separation / Boundary Layer Separation
If you are preparing or want to prepare for GATE 2019, then you have come to the right pla...
published: 26 Aug 2018
GATE 2019 | Fluid Mechanics | Flow Separation / Boundary Layer Separation
GATE 2019 | Fluid Mechanics | Flow Separation / Boundary Layer Separation
- Report rights infringement
- published: 26 Aug 2018
- views: 9897
If you are preparing or want to prepare for GATE 2019, then you have come to the right place 👍🏻 I regularly upload concised quality videos, specifically designed for Mechanical and Civil Engineering GATE Exam. I even solve the important questions of previous years GATE Exam. If you find my channel useful then please SUBSCRIBE it 🙏🏻 🙂 And do not forget to click the BELL 🛎 icon 🙂
#flowseparation
#fluidmechanics
#gatemechanical
#gate2019
#gatecivil
You even can ask any doubt related to GATE exam to #drgate, I will do my best to help you 🙂
4:17
What is a Boundary Layer? | Cause of Boundary Layer Formation | Types and Impact of Boundary Layers
Hi. In this video we look at what is a boundary layer and what causes a boundary layer to...
published: 02 Mar 2022
What is a Boundary Layer? | Cause of Boundary Layer Formation | Types and Impact of Boundary Layers
What is a Boundary Layer? | Cause of Boundary Layer Formation | Types and Impact of Boundary Layers
- Report rights infringement
- published: 02 Mar 2022
- views: 87965
Hi. In this video we look at what is a boundary layer and what causes a boundary layer to form on the surface of an object moving across a viscous fluid.
We look at the changes that happen because of the boundary layer and the 2 types of boundary layers: Laminar and Turbulent. We see the impact of the Boundary layer formation on different surfaces and how a turbulent boundary layer is still useful for a few applications.
hope its useful!!
Got Feedback! Mail it to [email protected]
Thank You! Please Watch and Subscribe!
11:32
Flow Separation and Reattachment — Lesson 4
This video lesson starts by describing how the velocity of the fluid in the boundary layer...
published: 24 Nov 2020
Flow Separation and Reattachment — Lesson 4
Flow Separation and Reattachment — Lesson 4
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- published: 24 Nov 2020
- views: 8812
This video lesson starts by describing how the velocity of the fluid in the boundary layer at the surface of the object is equal to the object’s velocity. When the fluid flows around an object, an adverse pressure layer forms that separates the boundary layer from the surface. Under certain circumstances a separated flow can become reattached to the surface again. This lesson is part of the Ansys Innovation Course: Real External Flows. To access this and all of our free, online courses — featuring additional videos, quizzes and handouts — visit Ansys Innovation Courses at https://www.ansys.com/courses.
16:43
Understanding Aerodynamic Drag
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published: 12 Jan 2021
Understanding Aerodynamic Drag
Understanding Aerodynamic Drag
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- published: 12 Jan 2021
- views: 965455
Get access to the extended version of this and other videos (without any ads) on Nebula - https://nebula.tv/videos/the-efficient-engineer-understanding-aerodynamic-drag-extended-version
Drag and lift are the forces which act on a body moving through a fluid, or on a stationary object in a flowing fluid. We call these aerodynamic forces (if the fluid is a gas) or hydrodynamic forces (if the fluid is a liquid).
This video is all about the drag force. There are two main causes of drag - first we have the pressure distribution around the object, which is particularly significant if flow separation occurs. And then we have the shear stresses acting on the object, which are most significant for streamlined bodies.
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15:11
Aside: Boundary Layer Separation
This clip explains why boundary layers separate and compares boundary layers with the Coue...
published: 27 May 2015
Aside: Boundary Layer Separation
Aside: Boundary Layer Separation
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- published: 27 May 2015
- views: 67931
This clip explains why boundary layers separate and compares boundary layers with the Couette and Poiseuille flow studied in chapter 3. It then explains some of the consequences for flow around wings and other objects.
0:50
Separation of Boundary layer
published: 27 Feb 2018
Separation of Boundary layer
Flow separation
All solid objects traveling through a fluid (or alternatively a stationary object exposed to a moving fluid) acquire a boundary layer of fluid around them where viscous forces occur in the layer of fluid close to the solid surface. Boundary layers can be either laminar or turbulent. A reasonable assessment of whether the boundary layer will be laminar or turbulent can be made by calculating the Reynolds number of the local flow conditions.
Flow separation occurs when the boundary layer travels far enough against an adverse pressure gradient that the speed of the boundary layer relative to the object falls almost to zero. The fluid flow becomes detached from the surface of the object, and instead takes the forms of eddies and vortices. In aerodynamics, flow separation can often result in increased drag, particularly pressure drag which is caused by the pressure differential between the front and rear surfaces of the object as it travels through the fluid. For this reason much effort and research has gone into the design of aerodynamic and hydrodynamic surfaces which delay flow separation and keep the local flow attached for as long as possible. Examples of this include the fur on a tennis ball, dimples on a golf ball, turbulators on a glider, which induce an early transition to turbulent flow regime; vortex generators on light aircraft, for controlling the separation pattern; and leading edge extensions for high angles of attack on the wings of aircraft such as the F/A-18 Hornet.
This page contains text from Wikipedia, the Free Encyclopedia - https://wn.com/Flow_separation
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