Transition, Minimum Critical, Minimum Transition, and Roughness Reynolds Numbers for Seven Blunt Bodies of Revolution in Flight between Mach Numbers of 1.72 and 15.1

1962 ◽  
Author(s):  
Neal Tetervin
Keyword(s):  
Reynolds Numbers ◽  
Bodies Of Revolution ◽  
Blunt Bodies ◽  
Mach Numbers

Heat Transfer in Rotating Serpentine Coolant Passage With Ribbed Walls at Low Mach Numbers

2015 ◽  
Vol 7 (1) ◽  
Author(s):  
Shang-Feng Yang ◽  
Je-Chin Han ◽  
Salam Azad ◽  
Ching-Pang Lee
Keyword(s):  
Heat Transfer ◽  
Mach Number ◽  
Reynolds Numbers ◽  
Working Fluid ◽  
Transfer Coefficients ◽  
Low Mach Number ◽  
Heat Transfer Coefficients ◽  
Rotation Numbers ◽  
Wide Range ◽  
Mach Numbers

This paper experimentally investigates the effect of rotation on heat transfer in typical turbine blade serpentine coolant passage with ribbed walls at low Mach numbers. To achieve the low Mach number (around 0.01) condition, pressurized Freon R-134a vapor is utilized as the working fluid. The flow in the first passage is radial outward, after the 180 deg tip turn the flow is radial inward to the second passage, and after the 180 deg hub turn the flow is radial outward to the third passage. The effects of rotation on the heat transfer coefficients were investigated at rotation numbers up to 0.6 and Reynolds numbers from 30,000 to 70,000. Heat transfer coefficients were measured using the thermocouples-copper-plate-heater regional average method. Heat transfer results are obtained over a wide range of Reynolds numbers and rotation numbers. An increase in heat transfer rates due to rotation is observed in radially outward passes; a reduction in heat transfer rate is observed in the radially inward pass. Regional heat transfer coefficients are correlated with Reynolds numbers for nonrotation and with rotation numbers for rotating condition, respectively. The results can be useful for understanding real rotor blade coolant passage heat transfer under low Mach number, medium–high Reynolds number, and high rotation number conditions.

Wake-Induced Unsteady Stagnation-Region Heat-Transfer Measurements

1992 ◽  
Author(s):  
P. J. Magari ◽  
L. E. LaGraff
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Reynolds Numbers ◽  
Edge Region ◽  
Isentropic Compression ◽  
Stagnation Region ◽  
Stagnation Line ◽  
Wide Range ◽  
Mach Numbers

An experimental investigation of wake-induced unsteady heat transfer in the stagnation region of a cylinder was conducted. The objective of the study was to create a quasi-steady representation of the stator/rotor interaction in a gas turbine using two stationary cylinders in crossflow. In this simulation, a larger cylinder, representing the leading-edge region of a rotor blade, was immersed in the wake of a smaller cylinder, represenung the trailing-edge region of a stator vane. Time-averaged and time-resolved heat-transfer results were obtained over a wide range of Reynolds numbers at two Mach numbers: one incompressible and one transonic. The tests were conducted at Reynolds numbers, Mach numbers and gas-to-wall temperature ratios characteristic of turbine engine conditions in an isentropic compression-heated transient wind tunnel (LICH tube). The augmentation of the heat transfer in the stagnation region due to wake unsteadiness was documented by comparison with isolated cylinder tests. It was found that the time-averaged heat-transfer rate at the stagnation line, expressed in terms of the Frossling number (Nu/√Re), reached a maximum independent of the Reynolds number. The power spectra and cross correlation of the heat-transfer signals in the stagnation region revealed the importance of large vortical structures shed from the upstream wake generator. These structures caused large positive and negative excursions about the mean heat-transfer rate in the stagnation region.

Blockage Corrections for Blunt-Based Bodies of Revolution

1968 ◽  
Vol 72 (696) ◽  
pp. 1058 ◽  
Author(s):  
W. A. Mair
Keyword(s):  
Correction Factor ◽  
Experimental Results ◽  
Base Pressure ◽  
Alternative Methods ◽  
Wind Tunnels ◽  
Maximum Diameter ◽  
Bodies Of Revolution ◽  
Blockage Correction ◽  
Mach Numbers ◽  
Experimental Values

Calvert has considered alternative methods of estimating the blockage corrections for blunt-based bodies of revolution in closed wind tunnels at low Mach numbers. His models were all of maximum diameter 152 mm, with an ellipsoidal nose section 203 mm long followed by a cylindrical afterbody. The ratio of overall length L to maximum diameter d varied from about 1.5 to 5.5. For each model the base pressure was measured in wind tunnels of two different sizes, so that the blockage correction factor e for the smaller tunnel could be derived for each model from the experimental results. These experimental values of e were compared with alternative theoretical estimates, using the methods given by Evans, Maskell and Pank-hurst and Holder.

Boundary-Layer Control as a Means of Reducing Drag on Fully Submerged Bodies of Revolution

1985 ◽  
Vol 107 (3) ◽  
pp. 342-347 ◽  
Author(s):  
B. Bar-Haim ◽  
D. Weihs
Keyword(s):  
Boundary Layer ◽  
Reynolds Numbers ◽  
Boundary Layer Transition ◽  
Boundary Layer Control ◽  
Layer Transition ◽  
Bodies Of Revolution ◽  
Boundary Layer Suction ◽  
Technique Optimization ◽  
Axisymmetric Bodies ◽  
Layer Control

The drag of axisymmetric bodies can be reduced by boundary-layer suction, which delays transition and can control separation. In this study, boundary-layer transition is delayed by applying a distributed suction technique. Optimization calculations were performed to define the minimal drag bodies at Reynolds numbers of 107 and 108. The saving in drag relative to optimal bodies with non-controlled boundary layers is shown to be 18 and 78 percent, at Reynolds numbers of 107 and 108, respectively.

scholarly journals Dynamics of Attached Cavities on Bodies of Revolution

1992 ◽  
Vol 114 (1) ◽  
pp. 93-99 ◽  
Author(s):  
S. L. Ceccio ◽  
C. E. Brennen
Keyword(s):  
Reynolds Numbers ◽  
Cavitation Number ◽  
The Body ◽  
Cavity Surface ◽  
Bodies Of Revolution ◽  
The Mean ◽  
Cavity Thickness ◽  
Cavity Closure ◽  
Axisymmetric Bodies ◽  
Single Cavity

Attached cavitation was generated on two axisymmetric bodies, a Schiebe body and a modified ellipsoidal body (the I. T. T. C. body), both with a 50.8 mm diameter. Tests were conducted for a range of cavitation numbers and for Reynolds numbers in the range of Re = 4.4 × 105 to 4.8 × 105. Partially stable cavities were observed. The steady and dynamic volume fluctuations of the cavities were recorded through measurements of the local fluid impedance near the cavitating surface suing a series of flush mounted electrodes. These data were combined with photographic observations. On the Schiebe body, the cavitation was observed to form a series of incipient spot cavities which developed into a single cavity as the cavitation number was lowered. The incipient cavities were observed to fluctuate at distinct frequencies. Cavities on the I. T. T. C. started as a single patch on the upper surface of the body which grew to envelope the entire circumference of the body as the cavitation number was lowered. These cavities also fluctuated at distinct frequencies associated with oscillations of the cavity closure region. The cavities fluctuated with Strouhal numbers (based on the mean cavity thickness) in the range of St = 0.002 to 0.02, which are approximately one tenth the value of Strouhal numbers associated with Ka´rma´n vortex shedding. The fluctuation of these stabilized partial cavities may be related to periodic break off and filling in the cavity closure region and to periodic entrainment of the cavity vapor. Cavities on both headforms exhibited surface striations in the streamwise direction near the point of cavity formation, and a frothy mixture of vapor and liquid was detected under the turbulent cavity surface. As the cavities became fully developed, the signal generated by the frothy mixture increased in magnitude with frequencies in the range of 0 to 50 Hz.

The Effect of Reynolds and Mach Number on End-Wall Profiling Performance

2010 ◽  
Author(s):  
Rau´l Va´zquez ◽  
Vicente Jerez Fidalgo
Keyword(s):  
Pressure Loss ◽  
Reynolds Numbers ◽  
Stagnation Pressure ◽  
Airfoil Surface ◽  
Pressure Losses ◽  
Physical Mechanisms ◽  
Wide Range ◽  
Mach Numbers ◽  
Turbine Airfoils ◽  
End Wall

This paper shows an experimental back-to-back comparison carried out between two annular cascades of identical turbine airfoils operating at the same flow conditions; one of them had axysimmetric endwalls and, the other, non-axysimmetric. The annular cascades consisted of 100 high lift, high aspect ratio and high turning blades that are characteristic of modern low pressure (LP) turbines. Upstream and downstream data were obtained with miniature pneumatic probes. The static pressure fields on the airfoil surface and the end-walls were measured with more than 200 sensors. The motivation of this work is to improve the understanding of profiled end-wall performance in the following three aspects: A. Explore the performance of profiled non-axysimmetric end-walls at off design conditions, namely its sensitivity to Reynolds and Mach numbers, analyzing how the turbine characteristics are modified. For that purpose, the experiment was carried out for a wide range of Reynolds numbers, extending from 120k to 315k, and exit Mach numbers, extending from 0.5 to 0.9. B. Determine experimentally the stagnation pressure loss improvement due to profiled non-axysimmetric end-walls in a relevant environment. C. Investigate further the physical mechanisms that govern the variation of stagnation pressure losses of profiled end-walls. CFD results are presented and are compared with experimental results in terms of total pressure loss, helicity and SKEH.

Investigation of flow asymmetry around axi-symmetric spiked blunt bodies in hypersonic speeds

2014 ◽  
Vol 118 (1200) ◽  
pp. 169-179 ◽  
Author(s):  
Mahmoud Y. M. Ahmed ◽  
N. Qin
Keyword(s):  
Cfd Simulation ◽  
Small Variation ◽  
Unstable Flow ◽  
Bodies Of Revolution ◽  
Axisymmetric Solution ◽  
Flow Asymmetry ◽  
Blunt Bodies ◽  
Flow Features ◽  
Hypersonic Speeds

Abstract The assumption that a zero-incidence flow around bodies of revolution is axisymmetric has been broadly adopted by many researchers, even for cases where the flow around such bodies becomes unstable. In this study, the validity of this assumption is revisited using CFD simulation. As a case study, the simulations of both stable and unstable hypersonic flows around spiked blunt bodies in 2D axisymmetric and full 3D computational domains are compared. It is found that, for the stable flow cases, the main flow features are apparently axisymmetric and the assumption is generally acceptable. However, some degree of asymmetry can be observed inside the shear layer in the separated region, causing small variation in the drag coefficient. For the unstable flow cases, the asymmetry of the flow features is much more significant. More importantly, the assumption that the flow is axisymmetric is found to overestimate the level of flow unsteadiness. The amplitude of temporal drag variation as predicted by the axisymmetric solution is higher than that predicted by the full 3D solution.

The Drag Due to Lift of Plane Wings at Subsonic Speeds

1966 ◽  
Vol 70 (665) ◽  
pp. 595-599 ◽  
Author(s):  
D. Gardner ◽  
J. Weir
Keyword(s):  
Wind Tunnel ◽  
Reynolds Numbers ◽  
Considerable Improvement ◽  
Induced Drag ◽  
Wind Tunnel Measurements ◽  
Lift Curve ◽  
Mach Numbers ◽  
Drag Factor

SummaryThis note outlines a method for the prediction of drag due to lift of plane wings at Mach numbers below drag divergence and Reynolds numbers above 106. The method is based on the correlation of a number of wind tunnel measurements in terms of the effect of viscosity on lift curve slope. A comparison is made of the accuracy of estimating the induced drag factor, k, using this method, with the method of ret. 1, and it is shown that considerable improvement has been made, and that, in general, the predicted value of k is within 10% of experiment.

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