# Wind flow analysis of a construction... Time-dependent or not?

**Teodor Penchev**Apr 28, 2013 4:16 AM

Dear SolidWorks Community,

I would like to ask you about your opinion on how to perform a **Fluid Flow Analysis (Fluid = Air)** of a structure that I modelled in SolidWorks. I would like to **investigate the effects of wind** (let's say **wind speed = 42 m/s [150 km/h or 95 miles/h]**) on a dual axis solar tracker.

I would like to know what the pressure on the front faces of the photovoltaic modules would be when they have different inclination angles (0°, 30°, 45°, 60° and 90°) with respect to the ground. I also want to investigate what the effect would be if there is a gap (0 to 10 cm) between the PV modules, I want to see the flow trajectories around the structure and through the gaps and how they change if I use these gaps, eventually how the Drag Force and the Pressure would change by introducing these gaps.

I also want to know what the Drag Force and the Lift Force would be. Finally, I want to import the results from the Fluid Flow Analysis to SolidWorks Simulation to see how my structure would deflect and what the stress would be. I could also perform an optimisation analysis to see e.g. if I could reduce the diameter of the supporting pole (use less material = cheaper).

So, here is my question: **should I perform a time-dependent (checking the time-dependent physical feature) analysis or not (using the default settings)**? **Is this a transient or a steady-state problem?**

I am a little bit confused about this concept. If I **were** interested in the cooling of the structure after it had been absorbing heat all day, then I know that I would have to use a time-dependent analysis. Let's say, I would want to know how many degrees cooler would my structure be after 5 minutes (starting from 70°C and ending where...). That is clear. But in my case, should I use time-dependent analysis? Actually, I just want to know the pressure and the force and then import the results in SolidWorks SImulation.

I am confused because I have seen many videos (e.g. this one or this one, see all parts) performing time-dependent analysis, e.g. the flow around a sphere where you can clearly see the turbulence when the Reynolds number is high (the higher the Reynolds number the higher the wind speed). This turbulence is not present for low Reynolds numbers. **In my case I want to simulate a wind speed of 150 km/h which is a high speed and the Reynolds number will also be high.** If I perform a time-dependent analysis would I see the turbulence? Would I see the turbulence if I perform a steady-state analysis? In other videos (e.g. this one, see the second part also) you can see an external flow analysis and the trajectories of the flow show no turbulence at all. Are the results correct? If I have to perform a time-dependent analysis, what should the time be set to and what should be the time step?

**What is your opinion, should I perform a time-dependent analysis or not? What would I miss if I perform a steady-state analysis? Would my results be still correct? Could you give me some tips on how to approach this problem?**

Thank you in advance for your tips!