======Pipe Constriction====== =====Experiments by Durst and Wang===== ---- ====Description==== The flow through a wall-mounted constriction in a pipe was studied, with geometry shown schematically in . Refractive index matching was employed to ensure that velocity measurements could be obtained in all regions inside of measured positions. Laser-Doppler-anemometry was used to obtain quantitative velocity information. The Reynolds number, based on constriction diameter, \(d\), and maximum velocity, \(U_{\max}\), was \(2.2\times 10^4\). {{ figs:case058:cas58-geom.png |Flow geometry}} ====Experimental Details==== ===Test Section and Experimental Techniques=== All the measurements for these experimental investigations were performed in the same closed-circuit pipe flow system employed by Durst et al.(1988), shown in . The working fluid was a mixture of two diesel oils, with a refractive index matching that of the quartz glass test section. The refractive index matching technique was used in order to prevent displacement of the measuring volume inside the test-section due to the curvature of the pipe walls. The test section comprised a 1 m long, 50mm diameter (\(D\)) quartz-glass pipe and a 25mm internal diameter (\(d\)) glass ring, located axisymmetrically in the pipe and yielding an area blockage ratio equal to 0.25. Two different lengths for this blockage are reported here, \(L=1\) mm and \(25\)mm (corresponding to \(L/d=0.04\) and \(1\), respectively). Fully developed symmetric inlet conditions were established at the entrance of the test section after a \(60 D\) entrance length and the outlet was \(36 D\) downstream of the obstacle. {{ figs:case058:cas58-exp.png | Schematic of the experiment}} The same one component LDA system used in Durst et al. (1988), employing a 15mW He-Ne laser with a forward light-scattering arrangement, was applied for velocity measurements. Signals were processed by a frequency counter (TSI Model 1990B), which operated in the continuous mode with eight cycles validation and 1% comparison error. In order to avoid the so called velocity bias, the data were sampled more than 2000 times at a regular frequency of 50Hz, with data rates ranging between 0.3 and 1.7 kHz. ====Available measurements==== Data available includes profiles of mean velocity and Reynolds stresses at a number of streamwise locations upstream and downstream of the pipe constriction. For the thin constriction (\(L/d=0.04\)) profiles are provided at \(x/H=-16\), \(-4\), \(-2\), \(-0.8\), \(0.04\), \(0.8\), \(2\), \(4\), \(6\), \(8\), \(10\), \(12\), \(16\), \(24\) and \(32\). For the \(L/d=1\) case profiles are provided at \(x/H=-16\), \(-4\), \(-0.8\), \(-0.04\), \(0.04\), \(0.8\), \(2\), \(4\), \(6\), \(8\), \(10\), \(12\), \(16\), and \(28\). Velocities are normalized with \(U_{\max}\), the maximum velocity along the pipe centreline. [[case058-plots|Sample plots]] of selected quantities are available. The data can be downloaded as compressed archives from the links below, or as individual files. * {{cdata:case058:pipc-allfiles.zip|pipc-allfiles.zip}} * {{cdata:case058:pipc-allfiles.tar.gz|pipc-allfiles.tar.gz}} ^ ^ Case A (\(L/d=1\)) ^ Case B (\(L/d=0.04\)) ^ | Mean \(U\) velocity | {{cdata:case058:ha_u.dat|ha_u.dat}} | {{cdata:case058:hb_u.dat|hb_u.dat}} | | Mean \(V\) velocity | {{cdata:case058:ha_v.dat|ha_v.dat}} | {{cdata:case058:hb_v.dat|hb_v.dat}} | | Mean \(W\) velocity | {{cdata:case058:ha_w.dat|ha_w.dat}} | {{cdata:case058:hb_w.dat|hb_w.dat}} | | \(\overline{u^2}\) stress | {{cdata:case058:ha_uu.dat|ha_uu.dat}} | {{cdata:case058:hb_uu.dat|hb_uu.dat}} | | \(\overline{v^2}\) stress | {{cdata:case058:ha_vv.dat|ha_vv.dat}} | {{cdata:case058:hb_vv.dat|hb_vv.dat}} | | \(\overline{w^2}\) stress | {{cdata:case058:ha_ww.dat|ha_ww.dat}} | {{cdata:case058:hb_ww.dat|hb_ww.dat}} | | \(\overline{uv}\) stress | {{cdata:case058:ha_uv.dat|ha_uv.dat}} | {{cdata:case058:hb_uv.dat|hb_uv.dat}} | | Turbulent kinetic energy, \(k\) | {{cdata:case058:ha_k.dat|ha_k.dat}} | {{cdata:case058:hb_k.dat|hb_k.dat}} | ====References==== - Durst, F., Founti, M., Wang, A.B. (1988). Experimental investigation of the flow through an axisymmetric constriction. Turbulent Shear Flows 6, (Eds. J.-C. Andre, J. Cousteix, F. Durst, B.E. Launder, F.W. Schmidt, J.H. Whitelaw), Springer Verlag, Berlin. - Durst, F., Wang, A.B. (1989). Experimental and numerical investigation of the axisymmetric turbulent pipe flow over a wall-mounted thin obstacle. //Proc. 7th Int. Symp. on Turbulent Shear Flows//, Stanford University. ---- Indexed data: case : 058 title : Pipe constriction author* : Durst, Wang year : 1991 type : EXP flow_tag* : axisymmetric, separated, varying_cross_section