Impact of a jet on flat plate and the local nusselt number
hello,
I study the impact of a jet on a flat plate, as shown in Figure 1. The flat plate is maintained at a constant temperature of 393.16K and the air jet is 293.16K at the injection. --- Re=200k, U inlet= 152m /s and U outlet= 9.5m/s P inlet, outlet= P atm openFOAM 4.x Turbulence model: realizableK 30<y+<300 buoyantsimplefoam Thermodynamic package: Code:
https://image.noelshack.com/fichiers...826-002730.png I subsequently calculated the local nusselt according to the position of the heated plate, we observe the curve of Figure 2. https://image.noelshack.com/fichiers...826-002454.png However, the curves from the experimental data give rather this kind of curve figure 3. https://image.noelshack.com/fichiers...826-002959.png Does anyone have an idea? |
Maybe the figures could be included, at least I could not see any figures or links to them.
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Secondary vortices at high Reynolds numbers
Is it a round Jet?
I understand that you use Re=200000 in your simulation compared to Re=11000 in the experiment. You can find very good experimental data in "STAGNATION REGION HEAT TRANSFER OF A TURBULENT AXISYMMETRIC JET IMPINGEMENT" by Lee and Lee (1999). There you see that with higher Reynolds number a second peak emerges and you get a valley in the centre (yours is quite strong). So basically both the experiment and the simulation could be correct. The second peaks comes from a secondary vortex, for a detailed explanation have a look at "Vortical structures and heat transfer in a round impinging jet" by Hadžiabdić and Hanjalić (2008). It is amazing that a realizable-KEpsilon model can give you this secondary vortex structure. |
You are right, they are not the same Reynolds.
But also in Re=11k, i have the same peak in the curve. Its not about the fvschemes ? I will read those documents and i will coming back. Thanks a lot. |
I moved the thread because it is not related to the subject of the subforum Verification & Validiation (please read the sticked thread)
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In the center of your jet you have a stagnation point. In this point it is not possible to move away heat. This is the result you got from your simulation.
In a reality (at higher Re number ) the position of the stagnation point moves around. This lead to an overall heat transfer, but with a less steep peek. |
By the way, the wallHeatFlux does not represent the Nusselt number. You compare something with anything. For a scientific investigation, calculate the Nusselt number and plot it against the measurement results.
Furthermore, what do you mean with U_outlet = x m/s? It seems that you make some mistakes in your set-up too or at least you do not provide enough information for your study/analysis. |
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