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Streamline Plots in a cross section
Posted Feb 1, 2012, 9:40 a.m. EST Fluid & Heat, Microfluidics Version 4.2 7 Replies
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Hi,
I am Akshay, a student of Mechanical Engineering. I am using COMSOL 4.2 for my research in Microfluidics, and am currently working on the numerical simulation of a purely Electro-osmotic flow in a curved channel, that is a quadrant of an annulus between 2 cylinders. The flow simulations for my research require the streamline contours of the flow in the cross section of the channel. But I am right now able to plot the streamlines only along the axial path of the channel, that is along the circumference. Although I am getting the results correct, they are of a lesser importance to me, since I need to capture the formation of flow circulations in the c/s of the channel.
Can anyone please help me on this problem ?
Sincerely,
Akshay
I am Akshay, a student of Mechanical Engineering. I am using COMSOL 4.2 for my research in Microfluidics, and am currently working on the numerical simulation of a purely Electro-osmotic flow in a curved channel, that is a quadrant of an annulus between 2 cylinders. The flow simulations for my research require the streamline contours of the flow in the cross section of the channel. But I am right now able to plot the streamlines only along the axial path of the channel, that is along the circumference. Although I am getting the results correct, they are of a lesser importance to me, since I need to capture the formation of flow circulations in the c/s of the channel.
Can anyone please help me on this problem ?
Sincerely,
Akshay
7 Replies Last Post Feb 3, 2012, 9:10 a.m. EST
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Posted:
1 decade ago
Hi
have you studied all the streamline plot options, i.e. User Manual p1014 ++ (v4.2a "Streamline Plot")
I believe you have abot any option possible as described therein
--
Good luck
Ivar
have you studied all the streamline plot options, i.e. User Manual p1014 ++ (v4.2a "Streamline Plot")
I believe you have abot any option possible as described therein
--
Good luck
Ivar
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Posted:
1 decade ago
Hello
Thank you very much for responding. As suggested by you, I went through the methods of streamline plots. but I could not find any plot relevant to what i actually want.
I want to capture the streamlines in a cross section such that they will be generated only by the velocity components normal to the flow direction along the circumference. But the flow being 3-Dimensional, there exists an axial component too. Can such a generation of streamlines be possible ?
When I attempt to plot the streamlines in a 3D plot group format, I use the "selected boundaries" option. But to obtain in a cross section, I need only the 2 components. So I tried by defining the axial component to be 0, but still it being a 3D case, I am getting streamlines all along the flow, which I do not wish to have.
I also tried to plot them in a 2D plot group format, by representing only the normal components to the flow direction, but the plots require a surface to be defined. i right now have only the confining surfaces of the geometry, but I need a surface in the domain, that will be at an angle to the X-axis, normal to the circumferential direction. How do I generate plots in that case, if no such surface exists ? If I have to define a surface i.e. a boundary inside the domain, how do I do it ?
Thanks
Akshay
Thank you very much for responding. As suggested by you, I went through the methods of streamline plots. but I could not find any plot relevant to what i actually want.
I want to capture the streamlines in a cross section such that they will be generated only by the velocity components normal to the flow direction along the circumference. But the flow being 3-Dimensional, there exists an axial component too. Can such a generation of streamlines be possible ?
When I attempt to plot the streamlines in a 3D plot group format, I use the "selected boundaries" option. But to obtain in a cross section, I need only the 2 components. So I tried by defining the axial component to be 0, but still it being a 3D case, I am getting streamlines all along the flow, which I do not wish to have.
I also tried to plot them in a 2D plot group format, by representing only the normal components to the flow direction, but the plots require a surface to be defined. i right now have only the confining surfaces of the geometry, but I need a surface in the domain, that will be at an angle to the X-axis, normal to the circumferential direction. How do I generate plots in that case, if no such surface exists ? If I have to define a surface i.e. a boundary inside the domain, how do I do it ?
Thanks
Akshay
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Posted:
1 decade ago
Hi,
For your referenc,e I am attaching the image of the geometry file herewith.
Thanks again,
Akshay
For your referenc,e I am attaching the image of the geometry file herewith.
Thanks again,
Akshay
Attachments:
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Posted:
1 decade ago
Hi
Im not sure I catch your question fully, but cant you sue a plane projection (Data Set Cut plane) and then plot 2D and do a contour plot ? togett the normal direction you will need to compose with nx,y,z projected to the correct plane. Therefore I believe the easiest would be to cut your part by a series of planes passing by the axis, on these interna boundaries you have access to the normals too, and the projection calculation should then be done for you.
But again I'm not 100% I got your true issue
--
Good luck
Ivar
Im not sure I catch your question fully, but cant you sue a plane projection (Data Set Cut plane) and then plot 2D and do a contour plot ? togett the normal direction you will need to compose with nx,y,z projected to the correct plane. Therefore I believe the easiest would be to cut your part by a series of planes passing by the axis, on these interna boundaries you have access to the normals too, and the projection calculation should then be done for you.
But again I'm not 100% I got your true issue
--
Good luck
Ivar
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Posted:
1 decade ago
Hello,
Thanks for the help. You got the question right. I also managed to obtain the 2-D streamlines by using cut-plane method. But the problem is that the components of velocity I plot in the streamlines are cartesian, while I need to change the co-ordinate system now to obtain accurate results.
I tried changing the co-ordinate system using the cylindrical command. But it does not appear in my results data sets. I also tried to go through the user's guide for the same problem, where I found out that the frame of the system must match with the one used by physics interface.
I am not very clear about what this frame means. Also, the new co-ordinate system I wish to obtain is thus:
X = R-C, where R is the polar radius of each point on the mesh w.r.t the origin, and C is the radius of curvature, which is a constant, known quantity.
Y = C*theta, where theta is the angle made with positive X-axis, thus this co-ordinate will be along the circumference of the channel geometry I attached before.
Z co-ordinate remains as it is
Can such a system be possible in COMSOL 4.2 ? If yes, which type does it fit into, cylindrical, mapped, spherical etc. ?
Also ,is it possible to obtain the components of the velocities along these new co-ordinates as defined above ?
Thanks again !!
Akshay
Thanks for the help. You got the question right. I also managed to obtain the 2-D streamlines by using cut-plane method. But the problem is that the components of velocity I plot in the streamlines are cartesian, while I need to change the co-ordinate system now to obtain accurate results.
I tried changing the co-ordinate system using the cylindrical command. But it does not appear in my results data sets. I also tried to go through the user's guide for the same problem, where I found out that the frame of the system must match with the one used by physics interface.
I am not very clear about what this frame means. Also, the new co-ordinate system I wish to obtain is thus:
X = R-C, where R is the polar radius of each point on the mesh w.r.t the origin, and C is the radius of curvature, which is a constant, known quantity.
Y = C*theta, where theta is the angle made with positive X-axis, thus this co-ordinate will be along the circumference of the channel geometry I attached before.
Z co-ordinate remains as it is
Can such a system be possible in COMSOL 4.2 ? If yes, which type does it fit into, cylindrical, mapped, spherical etc. ?
Also ,is it possible to obtain the components of the velocities along these new co-ordinates as defined above ?
Thanks again !!
Akshay
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Posted:
1 decade ago
Hello,
Thanks for the help. You got the question right. I also managed to obtain the 2-D streamlines by using cut-plane method. But the problem is that the components of velocity I plot in the streamlines are cartesian, while I need to change the co-ordinate system now to obtain accurate results.
I tried changing the co-ordinate system using the cylindrical command. But it does not appear in my results data sets. I also tried to go through the user's guide for the same problem, where I found out that the frame of the system must match with the one used by physics interface.
I am not very clear about what this frame means. Also, the new co-ordinate system I wish to obtain is thus:
X = R-C, where R is the polar radius of each point on the mesh w.r.t the origin, and C is the radius of curvature, which is a constant, known quantity.
Y = C*theta, where theta is the angle made with positive X-axis, thus this co-ordinate will be along the circumference of the channel geometry I attached before.
Z co-ordinate remains as it is
Can such a system be possible in COMSOL 4.2 ? If yes, which type does it fit into, cylindrical, mapped, spherical etc. ?
Also ,is it possible to obtain the components of the velocities along these new co-ordinates as defined above ?
Thanks again !!
Akshay
you can define a new set of co ordinates system using the transformation you have mentioned from the definitons node and get the results for the same from the results node .. and as you know ypu can manipulate the results from results node as well. .. (dont forget to copy the results and then manipulate)
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Posted:
1 decade ago
Hi Mr. Santosh,
Thnaks a lot for your help and response. i have actually tried to do it using a cylindrical system from Definitions option, but there i get components as r, phi and z. Even those would work for me. But the thing is I define the system there, but it doesn't appear in the results to be modified. How do we bring the system in the results ? And how do we manipulate the results once we can see the system ? Is it possible to obtain the velocity components along the new co-ordinates ?
Else, if I choose not to use the cylindrical system and define the co-ordinates as you say, where in definitions should I find it ? Which type of system do these fit into, cylindrical, or mapped or which one ?
Thanks again.
Akshay
Thnaks a lot for your help and response. i have actually tried to do it using a cylindrical system from Definitions option, but there i get components as r, phi and z. Even those would work for me. But the thing is I define the system there, but it doesn't appear in the results to be modified. How do we bring the system in the results ? And how do we manipulate the results once we can see the system ? Is it possible to obtain the velocity components along the new co-ordinates ?
Else, if I choose not to use the cylindrical system and define the co-ordinates as you say, where in definitions should I find it ? Which type of system do these fit into, cylindrical, or mapped or which one ?
Thanks again.
Akshay