Analysis and Modeling of the Vortex Amplifier

1969 ◽  
Vol 91 (4) ◽  
pp. 755-763 ◽  
Author(s):  
R. T. Bichara ◽  
P. A. Orner
Keyword(s):  
Experimental Data ◽  
Steady State ◽  
Computer Program ◽  
Flow Regime ◽  
Incompressible Flow ◽  
Digital Computer ◽  
Input Output ◽  
Critical Dimensions ◽  
Fluid Properties ◽  
Output Characteristics

A model has been derived to predict the steady-state input-output characteristics of vortex amplifiers operating in the incompressible flow regime. The model was correlated with experimental data to affect prediction of the influence of the operating fluid properties and the vortex valve critical dimensions on the valve characteristics. The model has been implemented in a digital computer program which includes procedures for the design of vortex valves with specified flow and pressure turndown ratios and the design of vortex amplifiers with proportional (single-valued) characteristics.

Computer simulation of the steady-state input-output function of the cat medial gastrocnemius motoneuron pool

1991 ◽  
Vol 65 (4) ◽  
pp. 952-967 ◽  
Author(s):  
C. J. Heckman ◽  
M. D. Binder
Keyword(s):  
Experimental Data ◽  
Steady State ◽  
Motor Unit ◽  
Frequency Modulation ◽  
Motor Units ◽  
Medial Gastrocnemius ◽  
Output Function ◽  
Input Output ◽  
Motoneuron Pool ◽  
Random Variance

1. A pool of 100 simulated motor units was constructed in which the steady-state neural and mechanical properties of the units were very closely matched to the available experimental data for the cat medial gastrocnemius motoneuron pool and muscle. The resulting neural network generated quantitative predictions of whole system input-output functions based on the single unit data. The results of the simulations were compared with experimental data on normal motor system behavior in humans and animals. 2. We considered only steady-state, isometric conditions. All motoneurons received equal proportions of the synaptic input, and no feedback loops were operative. Thus the intrinsic properties of the motor unit population alone determined the form of the system input-output function. Expressing the synaptic input in terms of effective synaptic current allowed the simulated motoneuron input-output functions to be specified by well-known firing rate-injected current relations. The motor unit forces were determined from standard motor unit force-frequency relations, and the system output at any input level was assumed to be the linear sum of the forces of the active motor units. 3. The steady-state input-output function of the simulated motoneuron pool had a roughly sigmoidal shape that was quite different from those derived from previous recruitment models, which did not incorporate frequency modulation. Frequency modulation in combination with the skewed distribution of thresholds (low values much more frequent than high) restricted upward curvature to low input levels, whereas frequency modulation alone was responsible for the final gradual approach to the maximum force output. 4. Sensitivity analyses were performed to assess the importance of several assumptions that were required to deal with gaps and uncertainties in the available experimental data. The shape of the input-output function was not critically dependent on any of these assumptions, including those specifying linear summation of inputs and outputs. 5. A key assumption of the model was that systematic variance in motor unit properties was much more important than random variance for determining the input-output function. Addition of random variance via Monte Carlo techniques showed that this assumption was correct. These results suggest that the output of a motoneuron pool should be quite tolerant of random variance in the distribution of synaptic inputs and yet substantially altered by any systematic differences, such as unequal distribution of inputs among different motor unit types.(ABSTRACT TRUNCATED AT 400 WORDS)

A Design Basis for Vortex-Type Fluid Amplifiers Operating in the Incompressible Flow Regime

1970 ◽  
Vol 92 (2) ◽  
pp. 369-376 ◽  
Author(s):  
D. N. Wormley ◽  
H. H. Richardson
Keyword(s):  
Flow Regime ◽  
Incompressible Flow ◽  
Experimental Studies ◽  
Maximum Flow ◽  
Vortex Chamber ◽  
Control Flow ◽  
Port Area ◽  
Performance Specifications ◽  
Fluid Properties ◽  
Control Port

A rational procedure is developed for the design of a class of vortex amplifiers which operate in the incompressible flow regime. The procedure is based upon analytical and experimental studies conducted to determine the effects of fluid properties and geometry on vortex amplifier behavior. These studies indicate that the nondimensional amplifier characteristic is essentially independent of the maximum flow Reynolds number, vortex chamber height, and supply port area if each of these parameters is within a specified broad range of values. The nondimensional characteristic was found to depend fundamentally upon the chamber exit to outer periphery radius ratio and the control port area to exit port area ratio. A systematic method is provided for progressing from a set of desired amplifier performance specifications, which include maximum control and supply port pressure and flow requirements, to a specification of each critical amplifier dimension. Three-point predictions of the transfer characteristics are obtained and the characteristics are checked to determine if multiple values of total flow exist at the cutoff value of control flow. The measured performance of a planar vortex amplifier designed with the aid of the procedure was found to agree closely with the desired performance specifications.

Zero-Load Stability of Rotating Externally Pressurized Gas-Lubricated Journal Bearings

1970 ◽  
Vol 92 (2) ◽  
pp. 325-334 ◽  
Author(s):  
David P. Fleming ◽  
R. E. Cunningham ◽  
W. J. Anderson
Keyword(s):  
Experimental Data ◽  
Steady State ◽  
Digital Computer ◽  
Pressure Ratio ◽  
Journal Bearings ◽  
Small Eccentricity ◽  
Attitude Angle ◽  
Stability Data ◽  
Bearing Number ◽  
Load Stability

A small eccentricity analysis was performed for a bearing having two feeding planes, each of which is assumed to be a line source. Numerical results were obtained for a range of bearing number, pressure ratio, feeding parameter, and orifice recess volume by means of a digital computer. Steady-state load and attitude angle were obtained, as well as stability data. Stability decreased markedly with increasing recess volume; moreover, for large recess volume and low bearing number, an increase in pressure ratio decreased stability. There was no correlation between stability and steady-state attitude angle for any of the cases studied. Fair agreement was obtained with available experimental data.

Capturing Radial Mixing in Axial Compressors With CFD

2018 ◽  
Author(s):  
Lorenzo Cozzi ◽  
Filippo Rubechini ◽  
Matteo Giovannini ◽  
Michele Marconcini ◽  
Andrea Arnone ◽  
...  
Keyword(s):  
Experimental Data ◽  
Steady State ◽  
Strain Field ◽  
Axial Compressor ◽  
Radial Transport ◽  
Steady State Analysis ◽  
Axial Compressors ◽  
Aspect Ratios ◽  
Fluid Properties ◽  
State Analysis

Due to the generally high stage and blade count, the current standard industrially adopted to perform numerical simulations on multistage axial compressors is the steady-state analysis based on the Reynolds-averaged Navier-Stokes approach (RANS), where the coupling between adjacent rows is handled by means of mixing planes. In addition to the well-known limitations of a steady-state picture of the flow, namely its inherent inability to capture the potential interaction and the wakes from the upstream blades, there is another flow feature which is lost through a mixing-plane, and which is believed to be a major accountable for the radial mixing: the transport of stream-wise vorticity. Streamwise vorticity arises throughout a compressor for various reasons, mainly associated with secondary and tip-clearance flows. A strong link does exist between the strain field associated with the transported vortices and the mixing augmentation: the strain field increases both the area available for mixing and the local gradients in fluid properties, which provide the driving potential for mixing itself. Especially for the rear stages of a multistage axial compressor, due to high clearances and low aspect ratios, only accounting for the development along the meridional path of secondary and clearance flow structures it is possible to properly predict the spanwise mixing. In this work, the results of steady and unsteady RANS simulations on the high-pressure section of an industrial heavy-duty axial compressor are presented and compared with experimental data acquired during a test campaign. Adopting an unsteady full-annulus URANS approach, the enhanced radial mixing in the rear stages of the compressor is properly captured, obtaining a really good agreement with experimental data both in terms of total temperature and pressure outlet radial distributions. On the contrary, with a steady-state modelling, the radial transport is strongly underestimated, leading to results with marked departures from experiments. Examining what occurs across the inter-row interfaces for RANS and URANS solutions, a possible explanation for this underestimation is provided. In particular, as the stream-wise vorticity associated with clearance flows is one of the main drivers of radial mixing, restraining it by pitch-averaging the flow at mixing planes of a steady-state analysis is the reason why this simplified approach is not able to properly predict the radial transport of fluid properties in the rear part of the axial compressor.

A computer program for writing the steady-state rate equation for a multisubstrate enzymic reaction

1969 ◽  
Vol 47 (10) ◽  
pp. 941-944 ◽  
Author(s):  
R. O. Hurst
Keyword(s):  
Steady State ◽  
Computer Program ◽  
Rate Equation ◽  
Digital Computer ◽  
Memory Capacity ◽  
Enzymic Reaction ◽  
Steady State Rate ◽  
State Rate ◽  
Enzyme Species

The determinant procedure for deriving the rate equation for an enzymic mechanism has been converted into Fortran IV language for use with a digital computer. The distribution equations for three to nine enzyme species, which may interact along all possible pathways, can be determined readily, limited only by the size of the memory capacity of the computer employed. The method permits several mechanisms to be analyzed in a matter of a few minutes.

Predicting the Effect of Tire Tread Pattern Design on Thick Film Wet Traction

1977 ◽  
Vol 5 (1) ◽  
pp. 6-28 ◽  
Author(s):  
A. L. Browne
Keyword(s):  
Experimental Data ◽  
Network Design ◽  
Thick Film ◽  
Digital Computer ◽  
Analytical Tool ◽  
Design Practice ◽  
Pattern Design ◽  
Performance Results ◽  
Good Agreement

Abstract An analytical tool is presented for the prediction of the effects of changes in tread pattern design on thick film wet traction performance. Results are reported for studies in which the analysis, implemented on a digital computer, was used to determine the effect of different tread geometry features, among these being the number, width, and lateral spacing of longitudinal grooves and the angle of zigzags in longitudinal grooves, on thick film wet traction. These results are shown to be in good agreement with experimental data appearing in the literature and are used to formulate guidelines for tread groove network design practice.

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