**cfd**602

#W0030 人生苦短，推荐一种计算快速、结果准确、功能全面的建模方式！

18 days ago by aries1988

美国一直是一帮做气象的人员在做风资源，所以大家看到的解决方案都是气象模式。3tier公司使用中尺度建模，TVM气象差分诊断模式进行降尺度。AWS Truepower公司使用中尺度建模，OpenWind也是一个源于70年代的质量守恒小尺度模型。

欧洲则是CFD的天下，当年丹麦Bolund岛评测，几十个CFD模型同台竞技。

美国那两家公司去欧洲宣讲，你们CFD还没有我的Openwind建模准确。可是还是各玩各的。

mtd
eolien
cfd
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欧洲则是CFD的天下，当年丹麦Bolund岛评测，几十个CFD模型同台竞技。

美国那两家公司去欧洲宣讲，你们CFD还没有我的Openwind建模准确。可是还是各玩各的。

18 days ago by aries1988

On the harmonic interpolation scheme for the diffusivity coefficient -- CFD Online Discussion Forums

4 weeks ago by aries1988

Hi Kathrin, I think that Ben's answer can be considered quite exhaustive. This kind of interpolation was indeed introduced in finite volume calculation to account for very sharp changes in the diffusive transport coefficient (think about heat conduction through anisotropic or in general composite materials). Concerning CFD, I can tell you that for High-Re incompressible turbulent flows (RANS/URANS modeling, without heat transfer) I've found no benefits in using harmonic interpolation instead of the linear one (in addition the harmonic scheme seems to be slightly more unstable). Of course, things may be different when heat transfer is involved, so you have definitely to try it for your case!

cfd
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4 weeks ago by aries1988

10 Best Stock Trading Platforms For Mac

cfd
mac
trade
finance

9 weeks ago by PBR

If you want to trade stocks from the comfort of your Mac, we've looked at the best stock trading platforms for Mac in 2019 to help you succeed. Stock

9 weeks ago by PBR

Uncertainty and Error in CFD Simulations

12 weeks ago by aries1988

Uncertainty and Error are commonly used interchangeably in everyday language. Here we follow the definitions of the AIAA Guidlines:

Uncertainty is defined as:

"A potential deficiency in any phase or activity of the modeling process that is due to the lack of knowledge." (AIAA G-077-1998)

Error is defined as:

A recoqnizable deficiency in any phase or activity of modeling and simulation that is not due to lack of knowledge. (AIAA G-077-1998)

cfd
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definition
Uncertainty is defined as:

"A potential deficiency in any phase or activity of the modeling process that is due to the lack of knowledge." (AIAA G-077-1998)

Error is defined as:

A recoqnizable deficiency in any phase or activity of modeling and simulation that is not due to lack of knowledge. (AIAA G-077-1998)

12 weeks ago by aries1988

Using CFD to Help Increase the Safety of Driverless Cars

july 2019 by aries1988

Pointwise uses a multiple block approach simplifying complex CFD studies into modular grids that can easily be linked together. This approach gives users full control of the process, from the smallest element to the largest, and enables them to troubleshoot and improve grid quality early in the process. It also saves time and increases accuracy by allowing the reuse of grids in different configurations for additional CFD studies.

“For the motorway study, I did not have to re-mesh the car. I did not have to re-extrude viscous layers or re-mesh the volume,“ says Khalil. “It saves a remarkable amount of time and ensures that the results are exactly the same because we’re using the exact same data and mesh. Pointwise’s T-Rex feature was also critical to accurately capturing the boundary layer flow, which is especially important for turbulence studies.”

cfd
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“For the motorway study, I did not have to re-mesh the car. I did not have to re-extrude viscous layers or re-mesh the volume,“ says Khalil. “It saves a remarkable amount of time and ensures that the results are exactly the same because we’re using the exact same data and mesh. Pointwise’s T-Rex feature was also critical to accurately capturing the boundary layer flow, which is especially important for turbulence studies.”

july 2019 by aries1988

Case Study: CFD and AI Can Aid Driverless Cars | Another Fine Mesh

july 2019 by aries1988

Working with his professors and advisors, Khalil began by gathering data about road conditions on the UK’s M1 roadway such as traffic patterns, accidents, winds, and speed. He then used Pointwise to create individual high-fidelity meshes for the subject car and a variety of vehicles. After inputting the road conditions and running simulations on the individual aerodynamics of the main vehicle, he joined all the meshes together using Pointwise’s multiple block feature for the final study of how the moving parts interacted together.

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july 2019 by aries1988

Implementation of boundary conditions for FVM -- CFD Online Discussion Forums

july 2019 by aries1988

[4] WHAT IS THE DIFFERENCE BETWEEN IMPLICIT AND EXPLICIT TREATMENT OF BOUNDARY CONDITIONS AND HOW DOES IT EFFECT THE DISCRETIZED EQUATION? I.E. HOW IS THE DIAGONAL INFLUENCED AND AND WHAT ABOUT THE EXPLICIT SOURCE TERM DUE TO THE BOUNDARY CONDITION?

for boundary cells the face value is "replaced" by the particular boundary assumption. Thus, when re-arranging the variables, you have the choice to either put the contribution in the source or in the matrix or to split it. Generally spoken, larger source terms (explicit) will slow convergence down.

explained
cfd
for boundary cells the face value is "replaced" by the particular boundary assumption. Thus, when re-arranging the variables, you have the choice to either put the contribution in the source or in the matrix or to split it. Generally spoken, larger source terms (explicit) will slow convergence down.

july 2019 by aries1988

Free Tools and Resources

july 2019 by cdwillie76

@AmberleyBabbage @feedly Since I see you are interested in Kanban and Excel, check out this link:

metrics
cfd
velocity
excel
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july 2019 by cdwillie76

SOLUTION TECHNIQUES

july 2019 by aries1988

Coupled Equations

The momentum and continuity equations are linked, in that the momentum equations share the pressure, and the velocities (and pressure via the density in compressible flows) enter the continuity equation.

There is no direct equation for the pressure. The task of all CFD codes is to join the variable without an equation (pressure), to the equation without a variable (continuity).

PHOENICS does this using a variant of the SIMPLE algorithm, namely SIMPLEST (= SIMPLEShorTened).

cfd
The momentum and continuity equations are linked, in that the momentum equations share the pressure, and the velocities (and pressure via the density in compressible flows) enter the continuity equation.

There is no direct equation for the pressure. The task of all CFD codes is to join the variable without an equation (pressure), to the equation without a variable (continuity).

PHOENICS does this using a variant of the SIMPLE algorithm, namely SIMPLEST (= SIMPLEShorTened).

july 2019 by aries1988

CONVERG.HTM

july 2019 by aries1988

Linear relaxation is almost always preferable to the false-time-step alternative. The reason is that the appropriate value for this time step is hard to choose; and what has been found suitable for one size of domain may be entirely unsuitable for another, even though other aspects of the flow may be identical.

A common error of inexperienced users is to set very small values of the false time step, e.g. 1.0e-3 sec for the velocity. They then find that the oscillations which have alarmed them disappear; and they are comforted by the apparently smooth progress of the solution procedure, not recognising that it is proceeding so slowly that an intolerably large number of sweeps will be needed to attain the true solution.

For a wind-farm simulation for example, in which a 10 km width and a 10 km/sec wind imply that effects take 1000 sec to be convected across the domain, even a 1.0 sec false time step imposes a severe delay on the attainment of the correct solution.

cfd
explained
A common error of inexperienced users is to set very small values of the false time step, e.g. 1.0e-3 sec for the velocity. They then find that the oscillations which have alarmed them disappear; and they are comforted by the apparently smooth progress of the solution procedure, not recognising that it is proceeding so slowly that an intolerably large number of sweeps will be needed to attain the true solution.

For a wind-farm simulation for example, in which a 10 km width and a 10 km/sec wind imply that effects take 1000 sec to be convected across the domain, even a 1.0 sec false time step imposes a severe delay on the attainment of the correct solution.

july 2019 by aries1988

CONVERGENCE MONITORING AND CONTROL

july 2019 by aries1988

The most widely-known technique for achieving convergence is the use of relaxation. This slows down (relaxes) the changes made to the variables from sweep to sweep. Relaxation does NOT alter the final solution, only the way in which it is achieved. Two types of relaxation are available: linear and false timestep.

explained
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july 2019 by aries1988

Cumulative Flow Diagram

agile
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continuous
cumulative

june 2019 by rlmflores

Cumulative Flow Diagram present information about status of work but also it helps to spot issues that a team may be facing. This is real power of CFD.

june 2019 by rlmflores

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