EBookClubs

Read Books & Download eBooks Full Online

EBookClubs

Read Books & Download eBooks Full Online

Book Experimental Study of Boundary Layer Transition with Elevated Freestream Turbulence on a Heated Flat Plate

Download or read book Experimental Study of Boundary Layer Transition with Elevated Freestream Turbulence on a Heated Flat Plate written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-24 with total page 268 pages. Available in PDF, EPUB and Kindle. Book excerpt: A detailed investigation to document momentum and thermal development of boundary layers undergoing natural transition on a heated flat plate was performed. Experimental results of both overall and conditionally sampled characteristics of laminar, transitional, and low Reynolds number turbulent boundary layers are presented. Measurements were acquired in a low-speed, closed-loop wind tunnel with a freestream velocity of 100 ft/s and zero pressure gradient over a range of freestream turbulence intensities (TI) from 0.4 to 6 percent. The distributions of skin friction, heat transfer rate and Reynolds shear stress were all consistent with previously published data. Reynolds analogy factors for R(sub theta) is less than 2300 were found to be well predicted by laminar and turbulent correlations which accounted for an unheated starting length. The measured laminar value of Reynolds analogy factor was as much as 53 percent higher than the Pr(sup -2/3). A small dependence of turbulent results on TI was observed. Conditional sampling performed in the transitional boundary layer indicated the existence of a near-wall drop in intermittency, pronounced at certain low intermittencies, which is consistent with the cross-sectional shape of turbulent spots observed by others. Non-turbulent intervals were observed to possess large magnitudes of near-wall unsteadiness and turbulent intervals had peak values as much as 50 percent higher than were measured at fully turbulent stations. Non-turbulent and turbulent profiles in transitional boundary layers cannot be simply treated as Blasius and fully turbulent profiles, respectively. The boundary layer spectra indicate predicted selective amplification of T-S waves for TI is approximately 0.4 percent. However, for TI is approximately 0.8 and 1.1 percent, T-S waves are localized very near the wall and do not play a dominant role in transition process. Sohn, Ki-Hyeon and Reshotko, Eli Unspecified Center NASA-CR-187068, NAS 1.26:187068 NAG3-...

Book An Experimental Study of Boundary Layer Transition

Download or read book An Experimental Study of Boundary Layer Transition written by Henry William Bennett and published by . This book was released on 1953 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book An Experimental Investigation of the Effect of Free Stream Turbulence on the Turbulent Boundary Layer Growth

Download or read book An Experimental Investigation of the Effect of Free Stream Turbulence on the Turbulent Boundary Layer Growth written by Alexander Vladimir Lisin and published by . This book was released on 1958 with total page 164 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Free Stream Turbulence and Concave Curvature Effects on Heated Transitional Boundary Layers

Download or read book Free Stream Turbulence and Concave Curvature Effects on Heated Transitional Boundary Layers written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-24 with total page 286 pages. Available in PDF, EPUB and Kindle. Book excerpt: An experimental investigation of the transition process on flat-plate and concave curved-wall boundary layers for various free-stream turbulence levels was performed. Results show that for transition of a flat-plate, the two forms of boundary layer behavior, identified as laminar-like and turbulent-like, cannot be thought of as separate Blasius and fully-turbulent profiles, respectively. Thus, simple transition models in which the desired quantity is assumed to be an average, weighted on intermittency, of the theoretical laminar and fully turbulent values is not expected to be successful. Deviation of the flow identified as laminar-like from theoretical laminar behavior is shown to be due to recovery after the passage of a turbulent spot, while deviation of the flow identified as turbulent-like from the full-turbulent values is thought to be due to incomplete establishment of the fully-turbulent power spectral distribution. Turbulent Prandtl numbers for the transitional flow, computed from measured shear stress, turbulent heat flux and mean velocity and temperature profiles, were less than unity. For the curved-wall case with low free-stream turbulence intensity, the existence of Gortler vortices on the concave wall within both laminar and turbulent flows was established using liquid crystal visualization and spanwise velocity and temperature traverses. Transition was found to occur via a vortex breakdown mode. The vortex wavelength was quite irregular in both the laminar and turbulent flows, but the vortices were stable in time and space. The upwash was found to be more unstable, with higher levels of u' and u'v', and lower skin friction coefficients and shape factors. Turbulent Prandtl numbers, measured using a triple-wire probe, were found to be near unity for all post-transitional profiles, indicating no gross violation of Reynolds analogy. No evidence of streamwise vortices was seen in the high turbulence intensity case. Kim, J. and Simon, T. W. Unspecified Cen...

Book Influence of Free stream Disturbances on Boundary layer Transition

Download or read book Influence of Free stream Disturbances on Boundary layer Transition written by William D. Harvey and published by . This book was released on 1978 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Testing of Transition region Models

Download or read book Testing of Transition region Models written by Bart A. Singer and published by . This book was released on 1991 with total page 88 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Direct Numerical Simulation of Transitional and Turbulent Flow Over a Heated Flat Plate Using Finite Difference Schemes

Download or read book Direct Numerical Simulation of Transitional and Turbulent Flow Over a Heated Flat Plate Using Finite Difference Schemes written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-02 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt: The work in this report was conducted at NASA Ames Research Center during the period from August 1993 to January 1995 deals with the direct numerical simulation of transitional and turbulent flow at low Mach numbers using high-order-accurate finite-difference techniques. A computation of transition to turbulence of the spatially-evolving boundary layer on a heated flat plate in the presence of relatively high freestream turbulence was performed. The geometry and flow conditions were chosen to match earlier experiments. The development of the momentum and thermal boundary layers was documented. Velocity and temperature profiles, as well as distributions of skin friction, surface heat transfer rate, Reynolds shear stress, and turbulent heat flux were shown to compare well with experiment. The numerical method used here can be applied to complex geometries in a straightforward manner. Madavan, Nateri K. Ames Research Center NCC2-755...

Book Modeling of the Heat Transfer in Bypass Transitional Boundary layer Flows

Download or read book Modeling of the Heat Transfer in Bypass Transitional Boundary layer Flows written by Frederick F. Simon and published by . This book was released on 1991 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Experimental Investigation of Boundary Layer Transition on a Flat Plate with a Point Heat Source at the Leading Edge

Download or read book Experimental Investigation of Boundary Layer Transition on a Flat Plate with a Point Heat Source at the Leading Edge written by W. J. McCroskey and published by . This book was released on 1962 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt: The addition of heat to the boundary layer of an insulated flat plate by means of a point heat source at the leading edge has been found to delay the transition of laminar flow to turbulence. This paper describes an experimental investigation of the variation of transition Reynolds number on a roughened flat plate model with a heat source of strength, Q, spanning the leading edge. The present problem is compared with the problem of an aerodynamically heated boundary layer on an insulated flat plate. Transition Reynolds number was found to increase with increasing S over a range equivalent to a Mach number variation of 0