Scientific Computing Department Seminars
06 Jun 2019
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You are invited to an SCD Seminar by –

 

Lei Wu, University of Strathclyde

Host: Xiaojun Gu, Engineering and Environment, SCD

 

Friday 11 October 2019 at 11:00-12:00

CR3 DL and via VC to CR02- R89 (S44) in RAL

Please join the seminar via Zoom, see instructions below

 

Can we find steady-state solutions to multiscale rarefied gas flows within dozens of iterations?

 

One of the central problems in the study of rarefied gas dynamics is to find the steady-state solution of the Boltzmann equation quickly. When the Knudsen number is large, the conventional iterative scheme can lead to convergence within a few iterations. However, when the Knudsen number is small, hundreds of thousands iterations are needed, and yet the ``converged'' solutions are prone to be contaminated by accumulated error and large numerical dissipation. Recently, we put forward a general synthetic iterative scheme (GSIS) to find the steady-state solutions of general rarefied gas flows within dozens of iterations at any Knudsen number. The key ingredient of our scheme is that the macroscopic equations, which are solved together with the Boltzmann equation and help to adjust the velocity distribution function, not only asymptotically preserve the Navier-Stokes limit in the framework of Chapman-Enskog expansion, but also contain Newton's law for stress and Fourier's law for heat conduction explicitly. The GSIS does not rely on the specific kinetic model/collision operator, it can be naturally extended to quickly find converged solutions for mixture flows and even flows involving chemical reactions. These two superior advantages are expected to accelerate the slow convergence in simulation of near-continuum flows via the direct simulation Monte Carlo method and its low-variance version.

 

../Documents/leiwu.jpgLei Wu is a Senior Lecturer at the University of Strathclyde. His research interest is in Rarefied (non-equilibrium) Gas Dynamics, in particular to construct efficient and accurate numerical schemes to solve Boltzmann equation for dilute gases and Enskog equation for dense gas/liquid-vapour multiphase flows, as well as kinetic modelling for polyatomic gas flows, with applications in high-altitude aerothermodynamics of space vehicles, MEMS, shale gas transportation, granular flows, multi-scale heat transfer in crystals, and thermal motion of quantum gases.

 

 

 

 

 

 

 

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You are invited to an SCD Seminar by –

 

Lei Wu, University of Strathclyde

Host: Xiaojun Gu, Engineering and Environment, SCD

 

Friday 11 October 2019 at 11:00-12:00

CR3 DL and via VC to CR02- R89 (S44) in RAL

Please join the seminar via Zoom, see instructions below

 

Can we find steady-state solutions to multiscale rarefied gas flows within dozens of iterations?

 

One of the central problems in the study of rarefied gas dynamics is to find the steady-state solution of the Boltzmann equation quickly. When the Knudsen number is large, the conventional iterative scheme can lead to convergence within a few iterations. However, when the Knudsen number is small, hundreds of thousands iterations are needed, and yet the ``converged'' solutions are prone to be contaminated by accumulated error and large numerical dissipation. Recently, we put forward a general synthetic iterative scheme (GSIS) to find the steady-state solutions of general rarefied gas flows within dozens of iterations at any Knudsen number. The key ingredient of our scheme is that the macroscopic equations, which are solved together with the Boltzmann equation and help to adjust the velocity distribution function, not only asymptotically preserve the Navier-Stokes limit in the framework of Chapman-Enskog expansion, but also contain Newton's law for stress and Fourier's law for heat conduction explicitly. The GSIS does not rely on the specific kinetic model/collision operator, it can be naturally extended to quickly find converged solutions for mixture flows and even flows involving chemical reactions. These two superior advantages are expected to accelerate the slow convergence in simulation of near-continuum flows via the direct simulation Monte Carlo method and its low-variance version.

Lei Wu, University of Strathclyde

Host: Xiaojun Gu, Engineering and Environment, SCD

 

Friday 11 October 2019 at 11:00-12:00

CR3 DL and via VC to CR02- R89 (S44) in RAL

Please join the seminar via Zoom, see instructions below

 

Can we find steady-state solutions to multiscale rarefied gas flows within dozens of iterations?

 

One of the central problems in the study of rarefied gas dynamics is to find the steady-state solution of the Boltzmann equation quickly. When the Knudsen number is large, the conventional iterative scheme can lead to convergence within a few iterations. However, when the Knudsen number is small, hundreds of thousands iterations are needed, and yet the ``converged'' solutions are prone to be contaminated by accumulated error and large numerical dissipation. Recently, we put forward a general synthetic iterative scheme (GSIS) to find the steady-state solutions of general rarefied gas flows within dozens of iterations at any Knudsen number. The key ingredient of our scheme is that the macroscopic equations, which are solved together with the Boltzmann equation and help to adjust the velocity distribution function, not only asymptotically preserve the Navier-Stokes limit in the framework of Chapman-Enskog expansion, but also contain Newton's law for stress and Fourier's law for heat conduction explicitly. The GSIS does not rely on the specific kinetic model/collision operator, it can be naturally extended to quickly find converged solutions for mixture flows and even flows involving chemical reactions. These two superior advantages are expected to accelerate the slow convergence in simulation of near-continuum flows via the direct simulation Monte Carlo method and its low-variance version.

 

Lei Wu is a Senior Lecturer at the University of Strathclyde. His research interest is in Rarefied (non-equilibrium) Gas Dynamics, in particular to construct efficient and accurate numerical schemes to solve Boltzmann equation for dilute gases and Enskog equation for dense gas/liquid-vapour multiphase flows, as well as kinetic modelling for polyatomic gas flows, with applications in high-altitude aerothermodynamics of space vehicles, MEMS, shale gas transportation, granular flows, multi-scale heat transfer in crystals, and thermal motion of quantum gases.

 

Phone one-tap:United Kingdom: +442034815237,,811799394# or +442039663809,,811799394#
Meeting URL: https://ukri.zoom.us/j/811799394
You can test your connection prior to the meeting here: https://ukri.zoom.us/test
Join by Telephone
For higher quality, dial a number based on your current location.
Dial:
United Kingdom: +44 203 481 5237 or +44 203 966 3809 or +44 131 460 1196 or +44 203 051 2874 or 0 800 031 5717 (Toll Free) or 0 800 260 5801 (Toll Free)
US: +1 669 900 6833 or +1 929 205 6099 or 877 853 5257 (Toll Free) or 888 475 4499 (Toll Free)
Meeting ID: 811 799 394
International numbers
Join from an H.323/SIP room system
H.323: 162.255.37.11 (US West)
162.255.36.11 (US East)
221.122.88.195 (China)
115.114.131.7 (India)
213.19.144.110 (EMEA)
103.122.166.55 (Australia)
209.9.211.110 (Hong Kong)
64.211.144.160 (Brazil)
69.174.57.160 (Canada)
207.226.132.110 (Japan)
Meeting ID: 811 799 394
SIP: 811799394@zoomcrc.com
Skype for Business (Lync)
https://ukri.zoom.us/skype/811799394
Skype on a SurfaceHub
SIP: 811799394@lync.zoom.us

https://d24cgw3uvb9a9h.cloudfront.net/static/93712/image/new/ZoomLogo_110_25.png 

Hi there,

Lomas, Georgia (STFC,DL,SC) is inviting you to a scheduled Zoom meeting.

Join Zoom Meeting

Phone one-tap:

United Kingdom: +442034815237,,811799394# or +442039663809,,811799394#

Meeting URL:

https://ukri.zoom.us/j/811799394

You can test your connection prior to the meeting here: https://ukri.zoom.us/test

Join by Telephone

For higher quality, dial a number based on your current location.

Dial:


United Kingdom: +44 203 481 5237 or +44 203 966 3809 or +44 131 460 1196 or +44 203 051 2874 or 0 800 031 5717 (Toll Free) or 0 800 260 5801 (Toll Free)
US: +1 669 900 6833 or +1 929 205 6099 or 877 853 5257 (Toll Free) or 888 475 4499 (Toll Free)

Meeting ID:

811 799 394

International numbers

Join from an H.323/SIP room system

H.323:

162.255.37.11 (US West)
162.255.36.11 (US East)
221.122.88.195 (China)
115.114.131.7 (India)
213.19.144.110 (EMEA)
103.122.166.55 (Australia)
209.9.211.110 (Hong Kong)
64.211.144.160 (Brazil)
69.174.57.160 (Canada)
207.226.132.110 (Japan)

Meeting ID:

811 799 394

SIP:

811799394@zoomcrc.com

Skype for Business (Lync)

https://ukri.zoom.us/skype/811799394

Skype on a SurfaceHub

SIP: 811799394@lync.zoom.us

 

 

Contact: Lomas, Georgia (STFC,DL,SC)