The prediction of turbulent boundary-layer separation Influenced by blowing /

The report presents an analysis predicting separation of a turbulent boundary layer over a cone-flare configuration with gas injected into the boundary layer ahead of separation point. Separation location and separation lengths are compared with experimental data obtained at Mach number of 6 and a range of Reynolds numbers. At the highest Reynolds numbers the extent of separation decreases with increasing Reynolds number. When compared to separation over cylinder-flare body it is found that the extent of separation is lower for the cone-flare configuration. (Author)."21 July 1971".Includes bibliographical references (page 13)The report presents an analysis predicting separation of a turbulent boundary layer over a cone-flare configuration with gas injected into the boundary layer ahead of separation point. Separation location and separation lengths are compared with experimental data obtained at Mach number of 6 and a range of Reynolds numbers. At the highest Reynolds numbers the extent of separation decreases with increasing Reynolds number. When compared to separation over cylinder-flare body it is found that the extent of separation is lower for the cone-flare configuration. (Author).Mode of access: Internet

Flow field measurements around an ogive-cylinder at angles of attack up to 15 degrees for mach numbers 3.5 and 4 /

The flow field was surveyed at one station (X/D = 6.5) on an ogive- cylinder having a tangent ogive nose with a fineness ratio of 4. The surveys were performed with pitot tubes and cone pressure probes at angles of attack of 0, 5, 10 and 15 degrees for Mach numbers 3.52 and 4.07. Surface static pressures were also measured. The results of the tests are presented in tabular and plotted form. Comparisons are made with inviscid flow fields calculations and with experimental results from other investigations."24 August 1972."Includes bibliographical references (pages 40-41)The flow field was surveyed at one station (X/D = 6.5) on an ogive- cylinder having a tangent ogive nose with a fineness ratio of 4. The surveys were performed with pitot tubes and cone pressure probes at angles of attack of 0, 5, 10 and 15 degrees for Mach numbers 3.52 and 4.07. Surface static pressures were also measured. The results of the tests are presented in tabular and plotted form. Comparisons are made with inviscid flow fields calculations and with experimental results from other investigations.Mode of access: Internet

The shock heights of static free jets /

The report describes the results of an experimental study involving a two-dimensional, underexpanded, free jet flowing into a static medium. The investigation was concerned with the determination of jet heights as a function of the nozzle flow properties. In support of this objective experimental results of two supersonic nozzles (Mach numbers of 2.89 and 2.99 and throat widths of 0.0335 inch and 0.0204 inch, respectively) are presented along with a complete data tabulation which includes photographs. A universal data correlation, expanded to include the axisymmetric jet case, is presented."11 January 1972."Includes bibliographical references (page 6)The report describes the results of an experimental study involving a two-dimensional, underexpanded, free jet flowing into a static medium. The investigation was concerned with the determination of jet heights as a function of the nozzle flow properties. In support of this objective experimental results of two supersonic nozzles (Mach numbers of 2.89 and 2.99 and throat widths of 0.0335 inch and 0.0204 inch, respectively) are presented along with a complete data tabulation which includes photographs. A universal data correlation, expanded to include the axisymmetric jet case, is presented.Mode of access: Internet

A cold flow field experimental study associated with a two-dimensional multiple nozzle /

A cold flow-field study of a rapid expansion, Mach 4.73, two-dimensional multiple nozzle array has been carried out in the hypersonic wind Tunnel. The nozzles are of the type used in a gas dynamic laser where the quality of the downstream flow field is important. The report examines the uniformity of the flow field in such a multiple nozzle array. Tests were conducted at supply conditions of 45 psia and 540 deg R. Pitot pressure, static pressure, and total temperature were measured along the axial, vertical, and horizontal centerlines within the nozzle and 21 nozzle exit heights downstream. Shadowgraph pictures provided qualitative flow field observations. The shock structure consisted of sidewall shocks, nozzle trailing edge shocks, and nozzle throat shocks. Viscous phenomena consisted of the boundary layers on the sidewalls and contoured walls, as well as the turbulent wakes caused by the trailing edges of the center nozzle blades. Mach number, static temperature, static density, and velocity profiles are presented. This flowfield information is useful to the prediction of the degradation of beam quality resulting from the non-homogeneity of a gas-dynamic-laser flowfield."1 July 1971."Includes bibliographical references (page 17)A cold flow-field study of a rapid expansion, Mach 4.73, two-dimensional multiple nozzle array has been carried out in the hypersonic wind Tunnel. The nozzles are of the type used in a gas dynamic laser where the quality of the downstream flow field is important. The report examines the uniformity of the flow field in such a multiple nozzle array. Tests were conducted at supply conditions of 45 psia and 540 deg R. Pitot pressure, static pressure, and total temperature were measured along the axial, vertical, and horizontal centerlines within the nozzle and 21 nozzle exit heights downstream. Shadowgraph pictures provided qualitative flow field observations. The shock structure consisted of sidewall shocks, nozzle trailing edge shocks, and nozzle throat shocks. Viscous phenomena consisted of the boundary layers on the sidewalls and contoured walls, as well as the turbulent wakes caused by the trailing edges of the center nozzle blades. Mach number, static temperature, static density, and velocity profiles are presented. This flowfield information is useful to the prediction of the degradation of beam quality resulting from the non-homogeneity of a gas-dynamic-laser flowfield.Mode of access: Internet

A forward facing step study: the step height less than the boundary-layer thickness /

An experimental investigation involving a thick, adiabatic, naturally turbulent, two-dimensional boundary layer undergoing separation has been completed at the Naval Ordnance Laboratory (NOL). Forward facing steps (with attached end plates) were used to induce boundary-layer separation for the particular case where the step heights, h, were less than the boundary-layer thickness, delta. The tests were conducted at a free-stream Mach number of 4.9 with a range of unit Reynolds numbers varying from 0.8 x 10 to the 6th power per foot to 4.0 x 10 to the 6th power per foot. The pressure distributions measured in the separated region ahead of the steps were found to be functions of both Re sub delta and h/delta for the turbulent boundary-layer separation case where h <delta."11 May 1973."Includes bibliographical references (pages 12-13)An experimental investigation involving a thick, adiabatic, naturally turbulent, two-dimensional boundary layer undergoing separation has been completed at the Naval Ordnance Laboratory (NOL). Forward facing steps (with attached end plates) were used to induce boundary-layer separation for the particular case where the step heights, h, were less than the boundary-layer thickness, delta. The tests were conducted at a free-stream Mach number of 4.9 with a range of unit Reynolds numbers varying from 0.8 x 10 to the 6th power per foot to 4.0 x 10 to the 6th power per foot. The pressure distributions measured in the separated region ahead of the steps were found to be functions of both Re sub delta and h/delta for the turbulent boundary-layer separation case where h <delta.Mode of access: Internet

Study of boundary-layer flows with pressure gradient and mass transfer by a simple integral method /

A refined Karman-Pohlhausen method previously generalized by Zien to include the effects of mass transfer is further explored and its application is extended to cases involving both pressure gradients and surface mass transfer. The case with piece-wise suction (or blowing) is also included. The study is restricted to plane, incompressible, laminar boundary layers. Configurations of flat plates and circular cylinders are chosen to illustrate the application of the method. Results are given mainly in terms of skin frictions, and they are presented entirely in closed forms. The calculations for the porous plate case are carried out using rather elaborate velocity profiles, but the results differ negligibly from previous ones with very simple profiles. A linear velocity profile is then used to carry out some exploratory calculations for more complex flows. The method is shown to be a potentially efficient tool for handling the problem of boundary-layer control by means of surface mass transfer. (Author)."22 March 1971."Includes bibliographical references (pages 24-25)A refined Karman-Pohlhausen method previously generalized by Zien to include the effects of mass transfer is further explored and its application is extended to cases involving both pressure gradients and surface mass transfer. The case with piece-wise suction (or blowing) is also included. The study is restricted to plane, incompressible, laminar boundary layers. Configurations of flat plates and circular cylinders are chosen to illustrate the application of the method. Results are given mainly in terms of skin frictions, and they are presented entirely in closed forms. The calculations for the porous plate case are carried out using rather elaborate velocity profiles, but the results differ negligibly from previous ones with very simple profiles. A linear velocity profile is then used to carry out some exploratory calculations for more complex flows. The method is shown to be a potentially efficient tool for handling the problem of boundary-layer control by means of surface mass transfer. (Author).Mode of access: Internet

Shock interaction surface pressures for hemispherical and conical bodies /

Transient pressures, induced by wind-tunnel simulated head-on blast wave interactions, have been measured on a hemisphere and on cones of 9-, 15- and 30-degree semivertex angles. Blast wave Mach numbers of 1.6 to 2.2, 2.2 to 5.85 and 2.7 to 4.4 were simulated at the free-stream Mach numbers of 3.1, 5.1 and 7, respectively. Measured pressure-time histories for the hemisphere were compared and found in agreement with histories predicted by McNamara's FLAME code. Peak overpressures for the cones were tested for agreement with values predicted by a simple theoretical method in which an assumption is made that the blast wave forms a Mach stem moving along the surface at a velocity whose axial component equals the velocity of the main blast wave. The effects of angle of attack and of nose blunting were also investigated with the nine-degree cone at a free-stream Mach number of 5.1. (Author)."16 February 1971."Includes bibliographical references (page 9)Transient pressures, induced by wind-tunnel simulated head-on blast wave interactions, have been measured on a hemisphere and on cones of 9-, 15- and 30-degree semivertex angles. Blast wave Mach numbers of 1.6 to 2.2, 2.2 to 5.85 and 2.7 to 4.4 were simulated at the free-stream Mach numbers of 3.1, 5.1 and 7, respectively. Measured pressure-time histories for the hemisphere were compared and found in agreement with histories predicted by McNamara's FLAME code. Peak overpressures for the cones were tested for agreement with values predicted by a simple theoretical method in which an assumption is made that the blast wave forms a Mach stem moving along the surface at a velocity whose axial component equals the velocity of the main blast wave. The effects of angle of attack and of nose blunting were also investigated with the nine-degree cone at a free-stream Mach number of 5.1. (Author).Mode of access: Internet

Turbulence measurements with a laser doppler velocimeter /

Turbulence measurements with a Laser Doppler Velocimeter (LDV) using the dual scatter or differential Doppler mode have been made in a subsonic, fully developed channel flow. The measurements were made using only those light scattering particles occurring naturally in air. Results include mean velocity profiles, turbulence intensities, Reynolds stress distributions and a skewness measurement of the velocity distribution function across the channel. Statistical techniques were used to obtain the various turbulence parameters. Guidelines have been established for the amount of data needed to obtain results with a specified accuracy and confidence level. Measurements have also been made to determine the particle-size distribution. An aerodynamic means was used to determine the size distribution, in contrast to the usual optical procedures. (Modified author abstract)."1 May 1973".Includes bibliographical references (pages 24-30)Turbulence measurements with a Laser Doppler Velocimeter (LDV) using the dual scatter or differential Doppler mode have been made in a subsonic, fully developed channel flow. The measurements were made using only those light scattering particles occurring naturally in air. Results include mean velocity profiles, turbulence intensities, Reynolds stress distributions and a skewness measurement of the velocity distribution function across the channel. Statistical techniques were used to obtain the various turbulence parameters. Guidelines have been established for the amount of data needed to obtain results with a specified accuracy and confidence level. Measurements have also been made to determine the particle-size distribution. An aerodynamic means was used to determine the size distribution, in contrast to the usual optical procedures. (Modified author abstract).Mode of access: Internet

Wrap-around-fin (WAF) pressure distribution /

The principal difference between a wrap around fin and a planar fin is that the WAF exhibits an induced rolling moment at zero degree angle of attack, while a straight fin has none. The Naval Ordnance Laboratory, along with other members of The Technical Cooperation Program, initiated a joint investigation into the causes of the induced roll moment. Measurements of the pressure distribution over both the convex and concave sides of a WAF showed that the primary difference in pressure across the fin occurred immediately behind the leading edge with the pressure on the convex side apparently being affected more by the curvature than that on the concave side. In general, for a WAF with fixed curvature, it appeared that the physical characteristic which would have the most effect on changing the roll moment would be the fin cross-sectional profile, especially the leading-edge profile. (Author)."1 October 1973."Includes bibliographical references (pages 18-21)The principal difference between a wrap around fin and a planar fin is that the WAF exhibits an induced rolling moment at zero degree angle of attack, while a straight fin has none. The Naval Ordnance Laboratory, along with other members of The Technical Cooperation Program, initiated a joint investigation into the causes of the induced roll moment. Measurements of the pressure distribution over both the convex and concave sides of a WAF showed that the primary difference in pressure across the fin occurred immediately behind the leading edge with the pressure on the convex side apparently being affected more by the curvature than that on the concave side. In general, for a WAF with fixed curvature, it appeared that the physical characteristic which would have the most effect on changing the roll moment would be the fin cross-sectional profile, especially the leading-edge profile. (Author).Mode of access: Internet