An aircraft is consist of many sub-parts , while estimating the Reynolds number and y+ value first layer height which length do we consider as the characteristic length to be used in the respective formulas ?
Hi Aamir Sultan,
if you want to calculate the Reynolds number to ensure if your flow is laminar or turbulent, I would take the shortest characteristic length possible. For an aircraft, the speed would be so high, that in the most cases the flow will be turbulent anyway, even with the shortest characteristic length. You can also check similar models from Mr. CFD (they have a youtube channel and facebook page). The best turbulent model to consider in such cases is the SST model, since it has good prediction near and far away from walls. Mostly, the kappa-epsilon and kappa-omega turbulent models will undeestimate the shear stress near the wall and will not predict well the separation behaviour of the flow, if such behaviour appears.
Best of luck!
Antoni Artinov
Dear Aamir Sultan
It really depends on the profile dimensions. Most commonly, the characteristic length (shortest length) that is commonly used to calculate Re be the distance from the leading edge of the object to the point of interest is taken.
Good luck
With respect
Dear Aamir Sultan ,
I agree with the question of Hiroaki Nishikawa . You should state the aim of the Reynolds number. For instance, when you want to analyze the formation, or controlling the separation bubble on the front side of the wings, you should choose the thickness of the airfoil. In another case, when you want to check the flow regime, I suggest you use the chord length to calculate the Reynolds number.
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