Flowrate Enforcement Question
******************* This email originates from outside Imperial. Do not click on links and attachments unless you recognise the sender. If you trust the sender, add them to your safe senders list https://spam.ic.ac.uk/SpamConsole/Senders.aspx to disable email stamping for this address. ******************* Hi, This may be a dumb question, but when we are setting a flowrate for a 3D1H problem (flow in the x-y and homogenous expansion in the Z). How would I set my Kinvis such that it follows the Reynolds number I am targeting? Within the parameters, enables the tag "Flowrate = 1.0". If I am doing a homogenous expansion in the z-direction, would I need to take into account LZ? or is this done automatically through the code? I am getting confused by the notations that is used within the user manual, and looking within the source code does not help me too much as both versions do not explicitly state to take into account the area of just the line. Any insight is appreciated, Dustin
Hi Dustin, In the case of 3DH1D with constant flowrate (in the z direction), kinvis should be scaled according to the user's definition of the Reynolds number. For instance, if the definition of the Reynolds number is Re = 2 * Ubulk * h / nu, then nu = 2 * Ubulk * h / Re. The flow-rate parameter actually refers to the volumetric flux - flow rate (m^3 s^-1) normalised by the surface area (m^2), so you wouldn't need to take into account LZ in this case. Hope this helps! Regards, Chi Hin ________________________________ From: nektar-users-bounces@imperial.ac.uk <nektar-users-bounces@imperial.ac.uk> on behalf of Ma, Ting-Hsuan <TIM48@pitt.edu> Sent: 09 May 2023 04:53 To: nektar-users <nektar-users@imperial.ac.uk> Subject: [Nektar-users] Flowrate Enforcement Question This email from TIM48@pitt.edu originates from outside Imperial. Do not click on links and attachments unless you recognise the sender. If you trust the sender, add them to your safe senders list<https://spam.ic.ac.uk/SpamConsole/Senders.aspx> to disable email stamping for this address. Hi, This may be a dumb question, but when we are setting a flowrate for a 3D1H problem (flow in the x-y and homogenous expansion in the Z). How would I set my Kinvis such that it follows the Reynolds number I am targeting? Within the parameters, enables the tag "Flowrate = 1.0". If I am doing a homogenous expansion in the z-direction, would I need to take into account LZ? or is this done automatically through the code? I am getting confused by the notations that is used within the user manual, and looking within the source code does not help me too much as both versions do not explicitly state to take into account the area of just the line. Any insight is appreciated, Dustin
Hi Chi Hin, Thank you for your response. This helps clarify my confusion a bit. However, in your example (as well as in Nektar), Ubulk is not a parameter that we can explicitly define. This means that Ubulk is calculated based on, <P> Flowrate = value </P> assignment, which is usually given as 1.0. From the definition given in the user-manual, my understanding is that the parameter tag, "Flowrate", equates to Ubulk. My 3DH1D has a constant flowrate in the X-direction (homogenous expansion in the z-direction). I have defined Flowrate = 1.0 and scale my kinematic viscosity accordingly. Based on your description of volumetric flux (without needing to account for the dimensional normalization), my kinematic viscosity should equate to U = flowrate tag. Would you say this assumption is correct? Side update: I was able to check the correctness of this assumption by extracting the velocity values at the inlet and integrating with respect to my inlet height, then dividing by the inlet height, which I expected to return the value I assign to "Flowrate". Best, Ting-Hsuan (Dustin) Ma ________________________________ From: Chan, Chi Hin <chi.chan19@imperial.ac.uk> Sent: Monday, May 15, 2023 3:57 PM To: Ma, Ting-Hsuan <TIM48@pitt.edu>; nektar-users <nektar-users@imperial.ac.uk> Subject: Re: Flowrate Enforcement Question Hi Dustin, In the case of 3DH1D with constant flowrate (in the z direction), kinvis should be scaled according to the user's definition of the Reynolds number. For instance, if the definition of the Reynolds number is Re = 2 * Ubulk * h / nu, then nu = 2 * Ubulk * h / Re. The flow-rate parameter actually refers to the volumetric flux - flow rate (m^3 s^-1) normalised by the surface area (m^2), so you wouldn't need to take into account LZ in this case. Hope this helps! Regards, Chi Hin ________________________________ From: nektar-users-bounces@imperial.ac.uk <nektar-users-bounces@imperial.ac.uk> on behalf of Ma, Ting-Hsuan <TIM48@pitt.edu> Sent: 09 May 2023 04:53 To: nektar-users <nektar-users@imperial.ac.uk> Subject: [Nektar-users] Flowrate Enforcement Question This email from TIM48@pitt.edu originates from outside Imperial. Do not click on links and attachments unless you recognise the sender. If you trust the sender, add them to your safe senders list<https://spam.ic.ac.uk/SpamConsole/Senders.aspx> to disable email stamping for this address. Hi, This may be a dumb question, but when we are setting a flowrate for a 3D1H problem (flow in the x-y and homogenous expansion in the Z). How would I set my Kinvis such that it follows the Reynolds number I am targeting? Within the parameters, enables the tag "Flowrate = 1.0". If I am doing a homogenous expansion in the z-direction, would I need to take into account LZ? or is this done automatically through the code? I am getting confused by the notations that is used within the user manual, and looking within the source code does not help me too much as both versions do not explicitly state to take into account the area of just the line. Any insight is appreciated, Dustin
Hi Dustin, Happy to hear that it is working now. You are right that the Flowrate parameter in nektar refers to Ubulk. It is also possible to post-process Ubulk using FieldConvert -m mean on the checkpoint files, hope this helps! Regards, Chi Hin ________________________________ From: Ma, Ting-Hsuan <TIM48@pitt.edu> Sent: 16 May 2023 16:11 To: Chan, Chi Hin <chi.chan19@imperial.ac.uk>; nektar-users <nektar-users@imperial.ac.uk> Subject: Re: Flowrate Enforcement Question Hi Chi Hin, Thank you for your response. This helps clarify my confusion a bit. However, in your example (as well as in Nektar), Ubulk is not a parameter that we can explicitly define. This means that Ubulk is calculated based on, <P> Flowrate = value </P> assignment, which is usually given as 1.0. From the definition given in the user-manual, my understanding is that the parameter tag, "Flowrate", equates to Ubulk. My 3DH1D has a constant flowrate in the X-direction (homogenous expansion in the z-direction). I have defined Flowrate = 1.0 and scale my kinematic viscosity accordingly. Based on your description of volumetric flux (without needing to account for the dimensional normalization), my kinematic viscosity should equate to U = flowrate tag. Would you say this assumption is correct? Side update: I was able to check the correctness of this assumption by extracting the velocity values at the inlet and integrating with respect to my inlet height, then dividing by the inlet height, which I expected to return the value I assign to "Flowrate". Best, Ting-Hsuan (Dustin) Ma ________________________________ From: Chan, Chi Hin <chi.chan19@imperial.ac.uk> Sent: Monday, May 15, 2023 3:57 PM To: Ma, Ting-Hsuan <TIM48@pitt.edu>; nektar-users <nektar-users@imperial.ac.uk> Subject: Re: Flowrate Enforcement Question Hi Dustin, In the case of 3DH1D with constant flowrate (in the z direction), kinvis should be scaled according to the user's definition of the Reynolds number. For instance, if the definition of the Reynolds number is Re = 2 * Ubulk * h / nu, then nu = 2 * Ubulk * h / Re. The flow-rate parameter actually refers to the volumetric flux - flow rate (m^3 s^-1) normalised by the surface area (m^2), so you wouldn't need to take into account LZ in this case. Hope this helps! Regards, Chi Hin ________________________________ From: nektar-users-bounces@imperial.ac.uk <nektar-users-bounces@imperial.ac.uk> on behalf of Ma, Ting-Hsuan <TIM48@pitt.edu> Sent: 09 May 2023 04:53 To: nektar-users <nektar-users@imperial.ac.uk> Subject: [Nektar-users] Flowrate Enforcement Question This email from TIM48@pitt.edu originates from outside Imperial. Do not click on links and attachments unless you recognise the sender. If you trust the sender, add them to your safe senders list<https://spam.ic.ac.uk/SpamConsole/Senders.aspx> to disable email stamping for this address. Hi, This may be a dumb question, but when we are setting a flowrate for a 3D1H problem (flow in the x-y and homogenous expansion in the Z). How would I set my Kinvis such that it follows the Reynolds number I am targeting? Within the parameters, enables the tag "Flowrate = 1.0". If I am doing a homogenous expansion in the z-direction, would I need to take into account LZ? or is this done automatically through the code? I am getting confused by the notations that is used within the user manual, and looking within the source code does not help me too much as both versions do not explicitly state to take into account the area of just the line. Any insight is appreciated, Dustin
participants (2)
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Chan, Chi Hin
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Ma, Ting-Hsuan