The Reynolds Number Effect On Cylinder Roof

It is important but hard to meet the law of Reynolds number similarity in windtunnel, so people wonder whether the results are credible. According to the researchbefore, the Reynolds number effect on curved structures is much remarkable. Wheninvestigate the Reynolds number effect on cylinder roof, people always use the resultsof circular cylinder, which has been studied for a long time. But in fact, there is muchessential difference between the two. A series of wind tunnel tests were performed toinvestigate the Reynolds number effect on circular cylinder, circular cylinder withsplitting plates, and cylinder roof in smooth flow. By means of comparative analysis,process of changes can be observedThe main contents in this paper are shown as following:1、The confirmation of test method. Some wind tunnel tests were performed tostudy the flow around circular cylinder. Reynolds number varies from8.30×104to1.41×106, Mean pressure distributions, drag coefficients, lift coefficients and Strouhalnumbers were calculated for comparative study with that in other papers. The resultsindicate that, this test method is valid, and the critical Reynolds number range is2.76×10~5≤Re≤3.86×10~5.2、The simulation of boundary conditions. A series of wind tunnel tests wasperformed on circular cylinder with splitting plates to simulate the boundary conditionsof cylinder roof. The results are based on comparative study. The splitting plate in fronthas more influence on the flow around the circular cylinder, especially the separation ofthe flow, leading to the steady of mean pressure distributions, and advance of fall ofdrag coefficients; while the splitting plate behind deters the vortex shedding, leading tothe Strouhal number keeping around zero.3、The confirmation of boundary conditions. Based on comparative analysis, thedifference between cylinder roof and circular cylinder is proved, and the effect ofboundary conditions of cylinder roof is studied.4、The study of sensitivity of a geometrical parameter on Reynolds number. Theeffect of rise to span ratio is studied by some wind tunnel tests. Research shows that, cylinder roofs with different rise have different Reynolds number effect. Above all, theReynolds number effect of lift coefficients is much more serious than that of dragcoefficients.5、The study of the influence of surface roughness. The circular cylinder and thecylinder roof are covered with standard commercial emery paper. The results show that,although surface roughness have an important effect on the flow regime, it can not beused for simulating the regime of high Reynolds number.