Total pressure

About: Total pressure is a research topic. Over the lifetime, 5199 publications have been published within this topic receiving 66658 citations.

Tip clearance effects in a turbine rotor : Part I : Pressure field and loss

Abstract: This paper presents an experimental investigation of the effects of the tip clearance flow in an axial turbine rotor. The effects investigated include the distribution and the development of the pressure, the loss, the velocity, and the turbulence fields. These flow fields were measured using the techniques of static pressure taps, rapid response pressure probes, rotating five-hole probes, and Laser Doppler Velocimeter. Part I of this paper covers the loss development through the passage, and the pressure distribution within the passage, on the blade surfaces, on the blade tip, and on the casing wall. Regions with both the lowest pressure and the highest loss indicate the inception and the trace of the tip leakage vortex. The suction effect of the vortex slightly increases the blade loading near the tip clearance region. The relative motion between the turbine blades and the casing wall results in a complicated pressure field in the tip region. The fluid near the casing wall experiences a considerable pressure difference across the tip. The highest total pressure drop and the highest total pressure loss were both observed in the region of the tip leakage vortex, where the loss is nearly twice as high as that near the passage vortex region. However, the passage vortex produces more losses than the tip leakage vortex in total. The development of the loss in turbine rotor is similar to that observed in cascades. Part II of this paper covers the velocity and the turbulence fields.Copyright © 2000 by ASME

Probe measurements and global model of inductively coupled Ar/CF4 discharges

Abstract: The electron energy distribution function (EEDF) is measured with a Langmuir probe in an inductively-coupled radio frequency (RF, 13.56 MHz) Ar/CF4 discharge over a pressure range 3-30 mTorr by changing the CF4 content from 0 to 20%, while keeping the power injected into the plasma at about 50 W. EEDFs measured at a pressure lower than 10 mTorr are bi-Maxwellian distributions over the measured CF4 content, while those at a pressure of 30 mTorr are Druyvesteyn ones in the presence of a small amount of CF4. The average electron energy slightly increases with CF4 content, while the electron density decreases. The decrease in the electron density with addition of CF4 is more prominent as the total pressure increases. Dependences of the electron density and the averaged electron energy on CF4 content are predicted in the global model.

Holdup and pressure drop with gas-liquid flow in a vertical pipe

Abstract: Vertical upward concurrent air-liquid flow was investigated under isothermal conditions in a test section of 1-in. schedule 40 pipe. Pressure drop was measured with a mercury manometer connected to two pressure taps 20 ft. apart in the section. Liquid was trapped between two quick shutoff valves activated by two solenoid valves. The liquid was druined from the section to provide the holdup data. Six liquids were used to determine the effect of density, viscosity, and surface tension. The experimental holdup, and two-phase pressure drop data were not in agreement with Lockhart-Martinelli type of correlation for horizontal flow. A statistical correlation for holdup was developed to include fluid physical properties, total mass velocity, and the air-liquid ratio entering the pipe. Similarly a pressure drop correlation was developed which expressed the two-phase pressure drop as a function of the slip velocity, liquid physical properties, and total mass velocity. This correlation showed an average percentage error of less than 15% between the observed and the calculated total pressure drop.

Internal‐tide energy over topography

Abstract: [1] The method used to separate surface and internal tides ultimately defines properties such as internal-tide generation and the depth structure of internal-tide energy flux. Here, we provide a detailed analysis of several surface-/internal-tide decompositions over arbitrary topography. In all decompositions, surface-tide velocity is expressed as the depth average of total velocity. Analysis indicates that surface-tide pressure is best expressed as the depth average of total pressure plus a new depth-dependent profile of pressure, which is due to isopycnal heaving by movement of the free surface. Internal-tide velocity and pressure are defined as total variables minus the surface-tide components. Corresponding surface- and internal-tide energy equations are derived that contain energy conversion solely through topographic internal-tide generation. The depth structure of internal-tide energy flux produced by the new decomposition is unambiguous and differs from that of past decompositions. Numerical simulations over steep topography reveal that the decomposition is self-consistent and physically relevant. Analysis of observations over Kaena Ridge, Hawaii; and the Oregon continental slope indicate O (50 W m−1) error in depth-integrated energy fluxes when internal-tide pressure is computed as the residual of pressure from its depth average. While these errors are small at major internal-tide generation sites, they may be significant where surface tides are larger and depth-integrated fluxes are weaker (e.g., over continental shelves).

Fractal analysis of flow resistance in tree-like branching networks with roughened microchannels

Abstract: In this work, the effective average height of the roughness elements, the relative increase of the pressure gradients, the relative decrease of the permeability are derived based on the fractal geometry theory and technique for laminar flow through tree-like branching networks with roughened channels. The relationships among the effective average height, the structural parameters and pressure drops as well as permeability are studied. It is found that the total pressure drop across a tree-like branching network with roughened channels is increased by a factor of 1/(1 − e)4, and the permeability for the network with roughened channels is decreased by a factor of (1 − e)2, where e is the relative roughness of surfaces of channels, compared to those with smooth channels.