This letter presents a series of curves for the backscattering cross section of an adsorbent sphere. The surface of the sphere is assumed to be one of the local reaction of point impedance, z, or of specific admittance, beta. The normalized backscattering cross section is given as a function of ka ranging from 0.2 to 21 and for beta ranging from 0 to infinity. (Author)

Topics: DTIC Archive, Lauchle,G C, PENNSYLVANIA STATE UNIV UNIVERSITY PARK APPLIED RESEARCH LAB, *BOUNDARY...

Basic hydrodynamic studies in turbomachinery and hydrodynamic drag reduction have been conducted. In the turbomachinery thrust area, the overall objective is to develop an improved understanding of the complex three- dimensional flows typical of incompressible rotor and stator flows; this effort has been primarily computational in nature. The second thrust area is axisymmetric turbulent flow drag reduction through microbubble injections. The third thrust area objective is to assess...

Topics: DTIC Archive, Lauchle, G C, PENNSYLVANIA STATE UNIV UNIVERSITY PARK APPLIED RESEARCH LAB,...

Boundary-layer transition and the fully-developed turbulent boundary are important contributors to sensor flow-induced self noise. The wall pressure fluctuations caused by these shear flows can be attenuated by localized fluid injection. Presented here is a vehicle forebody design concept that permits water to be injected into the transition region and adjacent turbulent boundary layer at prescribed volumetric flow rates. The injection flow rate may be tailored by a variable thickness porous...

Topics: DTIC Archive, Lauchle, G C, PENNSYLVANIA STATE UNIV UNIVERSITY PARK APPLIED RESEARCH LAB, *NOISE...

A series of water samples were collected from the test section of the Garfield Thomas 48-inch diameter water tunnel and analyzed for particulate shape, size, and elemental composition. These collections took place over a two week period of time and over a range of test section flow conditions. The analyses have shown that the standard deviation of the particulate average diameter is 2.1 microns, that they are typically non-spherical in shape with an average fineness ratio of 0.65, and that the...

Topics: DTIC Archive, Lauchle,G C, PENNSYLVANIA STATE UNIV UNIVERSITY PARK APPLIED RESEARCH LAB, *SAMPLING,...

A computational study is described where a 2-D elliptic cylinder is insonified by a plane, monochromatic acoustic wave. The elliptic cross section of the cylinder has a fineness ratio of 5:1, the incidence angle of the plane wave is 30 degrees and 60 degrees relative to the major axis of the ellipse, and ka = 20, where a is the major axis of the elliptic cross section and k is the acoustic wave number. The calculations are performed using the finite element method of solution for partial...

Topics: DTIC Archive, Lauchle, G C, PENNSYLVANIA STATE UNIV UNIVERSITY PARK APPLIED RESEARCH LAB, *ACOUSTIC...

It is well known that the static pressure coefficient values obtained from tests of axisymmetric bodies in, for example, a large water tunnel indicate the existence of tunnel wall interference. This interference is due to blockage experienced by the body operating within the boundaries of the test section walls, and to the skin friction on both the tunnel walls and the surface of the body, which in turn causes finite thickness boundary layers to develop. These factors result in a decrease in...

Topics: DTIC Archive, Lauchle,G C, PENNSYLVANIA STATE UNIV UNIVERSITY PARK APPLIED RESEARCH LAB,...

Acoustic measurements in the Applied Research Laboratory's 48-inch water tunnel are often-times performed using an ellipsoidal reflecting hydrophone which is submerged in a water-filled tank located on the east side of the test section. Acoustic energy originating within the test section then propagates to the receiver via the acoustically transparent viewing windows. The reflector of this hydrophone system was originally fabricated by welding together two ellipsoidal-shaped spinnings along...

Topics: DTIC Archive, Lauchle,G C, PENNSYLVANIA STATE UNIV UNIVERSITY PARK APPLIED RESEARCH LAB,...

With the recent interest in using two-microphone technique to measure acoustic intensity, fundamental questions arise when considering this method for hydroacoustic studies. The acoustic intensity generated by a hydrodynamic source is related solely to those pressure components that propagate. The basic questions are then, what influence does the nonpropagating hydrodynamic pressure fluctuations have on the intensity probe when used in the nearfield of the source and can their effect be removed...

Topics: DTIC Archive, Lauchle,G C, PENNSYLVANIA STATE UNIV UNIVERSITY PARK APPLIED RESEARCH LAB, *ACOUSTIC...

A theory is presented for the noise radiated by incompressible boundary-layer transition that occurs on an infinite, rigid flat plate. It is hypothesized that it is the intermittency of the boundary-layer flow within the transition zone that is dominant in noise production. Using Lighthill's analogy, it is shown that dipole, quadrupole, and octupole sources are generated. Under the assumption of low Mach number flow, the power spectral density per unit spanwise width of transition for the...

Topics: DTIC Archive, Lauchle,G C, PENNSYLVANIA STATE UNIV UNIVERSITY PARK APPLIED RESEARCH LAB, *BOUNDARY...

It is well known that the static pressure distribution of an axisymmetric body operating within the boundaries of a duct such as a wind or water tunnel test section is altered from that observed in a free stream because of solid blockage and horizontal buoyancy effects. Because potential flow solutions can account only for the solid blockage, auxiliary analysis must be performed to account for the viscous (horizontal buoyancy) effects. One such analysis has been performed by this author, where...

Topics: DTIC Archive, Lauchle,G C, PENNSYLVANIA STATE UNIV UNIVERSITY PARK APPLIED RESEARCH LAB, *DUCTS,...

A theory is presented for the noise radiated by incompressible boundary-layer transition that occurs on an infinite, rigid flat plate. It is hypothesized that it is the intermittency of the boundary-layer flow within the transition zone that is dominant in noise production. Using Lighthill's analogy, it is shown that dipole, quadrupole, and octupole sources are generated. The dipole sources are attributable to the shear stress fluctuations that occur in transitional flow while the others are...

Topics: DTIC Archive, Lauchle,G C, PENNSYLVANIA STATE UNIV UNIVERSITY PARK APPLIED RESEARCH LAB, *BOUNDARY...

The role of the fluctuating wall shear stress on the noise generated by incompressible boundary-layer transition was recently analyzed. The solutions of that analysis suggest that the shear stress mechanism generates hydrodynamic sound weakly in comparison say to the sound generated by a fully developed turbulent boundary layer flow. Because boundary-layer transition is a very unstable and non-steady flow, it is expected that other acoustic mechanisms exist. This paper examines one other;...

Topics: DTIC Archive, Lauchle,G C, PENNSYLVANIA STATE UNIV UNIVERSITY PARK APPLIED RESEARCH LAB, *FLOW...

A large (3.05m long x 0.32m diameter) heated-surface, axisymmetric body, designed for transition research in a 1.22m diameter water tunnel is described. Boundary layer transition data are presented as functions of the heating power supplied to the body and the total concentration of free-stream particulate matter in the water. Body surface temperatures range from 0 to 25 deg C over the ambient water temperature, and the total heat supplied ranges from 0 to 93.3 kW. Transition arc length...

Topics: DTIC Archive, Lauchle, G C, PENNSYLVANIA STATE UNIV UNIVERSITY PARK APPLIED RESEARCH LAB, *BOUNDARY...

Acoustic measurements performed with pressure sensors (microphones and hydrophones) can be subject to misinterpretation if the sensors are in contact with a turbulent boundary layer flow. This misinterpretation is a result of non-propagating pressure fields (flow noise) generated by the turbulent motions of the fluid. In this paper, a simple analysis is given whereby the flow noise response of a pressure sensor placed in a turbulent boundary layer flow can be estimated. If the purpose of the...

Topics: DTIC Archive, Lauchle,G C, PENNSYLVANIA STATE UNIV UNIVERSITY PARK APPLIED RESEARCH LAB, *TURBULENT...

The ARL (Penn State Univ.'s Applied Research Lab.) Heated Laminar flow (HLF) body is a streamlined body with a pointed nose. One of the experimental objectives for the ARL/HLF body is to provide for limited (low flow) stagnation point fluid ejection. Because fluid ejection can, in many instances, create laminar instabilities farther downstream, it is important to have a stagnation region geometry that helps minimize the enhancement of these instabilities. This is best achieved by using a...

Topics: DTIC Archive, Lauchle, G C, PENNSYLVANIA STATE UNIV STATE COLLEGE APPLIED RESEARCH LAB, *BOUNDARY...