Characteristics of a separating confluent boundary layer and the downstream wake

Measurements of pressure and velocity characteristics are presented and analyzed for flow over and downstream of a NACA 4412 airfoil equipped with a NACA 4415 single-slotted flap at high angle of attack and close to maximum lift. The flow remained attached over the main element while a large region of recirculating flow occurred over the aft 61 percent of the flap. The airfoil configuration was tested at a Mach number of 0.09 and a chord Reynolds number of 1.8x10 to the 6th power in the NASA Ames Research Center 7- by 10-Foot Wind Tunnel. Measurement of mean and fluctuation velocities were obtained in regions of recirculation and high turbulence intensity using 3-D laser velocimetry. In regions where the flow had a preferred direction and relatively low turbulence intensity, hot-wire anemometry was used. Emphasis was placed on obtaining characteristics in the confluent boundary layer, the region of recirculating flow, and in the downstream wake. Surface pressure measurements were made on the main airfoil, flap, wind tunnel roof and floor. It is thought likely that because the model is large when compared to the wind tunnel cross section, the wind tunnel floor and ceiling interference should be taken into account when the flow field is calculated

A microcomputer based frequency-domain processor for laser Doppler anemometry

A prototype multi-channel laser Doppler anemometry (LDA) processor was assembled using a wideband transient recorder and a microcomputer with an array processor for fast Fourier transform (FFT) computations. The prototype instrument was used to acquire, process, and record signals from a three-component wind tunnel LDA system subject to various conditions of noise and flow turbulence. The recorded data was used to evaluate the effectiveness of burst acceptance criteria, processing algorithms, and selection of processing parameters such as record length. The recorded signals were also used to obtain comparative estimates of signal-to-noise ratio between time-domain and frequency-domain signal detection schemes. These comparisons show that the FFT processing scheme allows accurate processing of signals for which the signal-to-noise ratio is 10 to 15 dB less than is practical using counter processors

Surface tension induced convection in encapsulated liquid metals in microgravity: Apollo-Soyuz test project experiment no. MA-041

This experiment was designed to determine the extent of surface tension induced convection caused by a steplike compositional variation in a liquid metal. Preliminary results are presented

Purification and electron cryomicroscopy of coronavirus particles.

Intact, enveloped coronavirus particles vary widely in size and contour, and are thus refractory to study by traditional structural means such as X-ray crystallography. Electron microscopy (EM) overcomes some problems associated with particle variability and has been an important tool for investigating coronavirus ultrastructure. However, EM sample preparation requires that the specimen be dried onto a carbon support film before imaging, collapsing internal particle structure in the case of coronaviruses. Moreover, conventional EM achieves image contrast by immersing the specimen briefly in heavy-metal-containing stain, which reveals some features while obscuring others. Electron cryomicroscopy (cryo-EM) instead employs a porous support film, to which the specimen is adsorbed and flash-frozen. Specimens preserved in vitreous ice over holes in the support film can then be imaged without additional staining. Cryo-EM, coupled with single-particle image analysis techniques, makes it possible to examine the size, structure and arrangement of coronavirus structural components in fully hydrated, native virions. Two virus purification procedures are described

Thermomagnetic Force in Polyatomic Gases

Journals published by the American Physical Society can be found at http://publish.aps.org