Experimental Study of Propeller-Induced Vibratory Pressures on Simple Surfaces and Correlation With Theoretical Predictions

1964 ◽  
Vol 8 (05) ◽  
pp. 15-28
Author(s):  
J. P. Breslin ◽  
T. Kowalski
Keyword(s):  
Free Space ◽  
Three Dimensional ◽  
Theoretical Treatment ◽  
Plate Boundaries ◽  
Practical Application ◽  
Finite Area ◽  
Experimental Procedure ◽  
Theoretical Predictions ◽  
Pressure Changes ◽  
Good Agreement

Vibratory pressures exerted on cylindrical and flat-plate boundaries due to a model propeller were measured at three advance coefficients. A number of "free-space" measurements also were made. All measurements were made by driving a propeller past fixed pressure gages. This method yielded curves of pressure changes which are entirely free from background noise. The magnitudes of the free-space pressures were found to be larger than one half the corresponding magnitudes measured by gages mounted flush in a large plate at equal clearances from the propeller. By postulating that the finite area of the gage diaphragm produces a partial image of the propeller (and hence a larger pressure than that in free space) an experimental procedure was devised for correcting for this finite-area effect yielding results in good agreement with theory. A theoretical treatment of this effect of finite gage size is given in Appendix 2. The decay of maximum amplitudes of vibrating pressures is shown by means of three-dimensional plots. The pressures were found to become vanishingly small within approximately one propeller diameter fore and aft of the center of the propeller. The comparison with theoretically calculated pressures and forces gives very close agreement for free-space pressures and reasonable agreement for forces on a cylindrical surface. The agreement of both pressures and forces with theory is excellent for operation near the design advance ratio. A strong plea is made for further experiments with ship models in an effort to develop design criteria for practical application.

A System of Selective Non Catalytic Reduction of NOx for Diesel Engine

2011 ◽  
Vol 201-203 ◽  
pp. 643-646 ◽  
Author(s):  
Bo Yan Xu ◽  
Hai Ying Tian ◽  
Jie Yang ◽  
De Zhi Sun ◽  
Shao Li Cai
Keyword(s):  
Catalytic Reduction ◽  
Three Dimensional ◽  
Exhaust Gas ◽  
Test Results ◽  
Practical Application ◽  
Three Dimensional Model ◽  
Reduction Efficiency ◽  
Different Temperatures ◽  
Reduction Of Nox ◽  
Good Agreement

SNCR (Selective Non Catalytic Reduction) system is proposed, with 40% methylamine aqueous solution as reducing agent to reduce NOx in diesel exhaust gas. The effect of injection position and volume on the reduction efficiency through the test bench is systematically researched. A three-dimensional model of a full-sized diesel SNCR system generated by CFD software FIRE is used to investigate the reduction efficiency under different temperatures. The simulated results have a good agreement with the test results, and it can be used to optimize SNCR system. The results can indicate the practical application of this technology.

Studies on the Three-Dimensional Temperature Transients in the Canine Prostate During Transurethral Microwave Thermal Therapy

2000 ◽  
Vol 122 (4) ◽  
pp. 372-379 ◽  
Author(s):  
Jing Liu ◽  
Liang Zhu ◽  
Lisa X. Xu
Keyword(s):  
Three Dimensional ◽  
Blood Perfusion ◽  
Thermal Therapy ◽  
Bioheat Transfer ◽  
Target Tissue ◽  
Urethral Wall ◽  
Theoretical Predictions ◽  
Closed Form Analytical Solution ◽  
Good Agreement

Thermal therapy of benign prostatic hyperplasia requires accurate prediction of the temperature distribution induced by the heating within the prostatic tissue. In this study, the Pennes bioheat transfer equation was used to model the transient heat transfer inside the canine prostate during transurethral microwave thermal therapy. Incorporating the specific absorption rate of microwave energy in tissue, a closed-form analytical solution was obtained. Good agreement was found between the theoretical predictions and in-vivo experimental results. Effects of blood perfusion and the cooling at the urethral wall on the temperature rise were investigated within the prostate during heating. The peak intraprostatic temperatures attained by application of 5, 10, or 15 W microwave power were predicted to be 38°C,41°C, and 44°C. Results from this study will help optimize the thermal dose that can be applied to target tissue during the therapy. [S0148-0731(00)01004-9]

Backward Extrusion of Internally Shaped Tubes From Round Billets

1984 ◽  
Vol 106 (2) ◽  
pp. 143-149 ◽  
Author(s):  
D. Y. Yang ◽  
C. H. Han
Keyword(s):  
Pure Aluminum ◽  
Three Dimensional ◽  
Mapping Function ◽  
Velocity Transformation ◽  
Backward Extrusion ◽  
Commercially Pure ◽  
Theoretical Predictions ◽  
Experimental Values ◽  
Punch Pressure ◽  
Good Agreement

An analytical method is proposed for estimating the steady-state punch pressure for three-dimensional backward extrusion (or piercing) of complicated internally shaped tubes from circular billets. A kinematically admissible velocity field is derived to formulate an upper-bound solution using velocity transformation and mapping function. The configuration of deforming boundary surfaces are determined by minimizing the extrusion power with respect to some chosen parameters. Experiments are carried out with commercially pure aluminum billets for internally shaped tubes at various reductions of area by using different sizes of shaped punches, such as square and regular hexagons. It is shown that the theoretical predictions for extrusion load are in good agreement with the experimental values.

A Simplified Method of Using Four-Hole Probes to Measure Three-Dimensional Flow Fields

1985 ◽  
Vol 107 (1) ◽  
pp. 31-35 ◽  
Author(s):  
N. Sitaram ◽  
A. L. Treaster
Keyword(s):  
Flat Plate ◽  
Three Dimensional ◽  
Flow Fields ◽  
Three Dimensional Flow ◽  
Dimensional Flow ◽  
Application Procedure ◽  
Simplified Method ◽  
Theoretical Predictions ◽  
Gradient Effects ◽  
Good Agreement

A simplified method of using four-hole probes to measure three-dimensional flow-fields is presented. This method is similar to an existing calibration and application procedure used for five-hole probes. The new method is demonstrated for two four-hole probes of different geometry. These four-hole probes and a five-hole probe are used to measure the turbulent boundary layer on a flat plate. The results from the three probes are in good agreement with theoretical predictions. The major discrepancies occur near the surface of the flat plate and are attributed to wall vicinity and velocity gradient effects.

scholarly journals Energy spectrum in the dissipation range of fluid turbulence

1997 ◽  
Vol 57 (1) ◽  
pp. 195-201 ◽  
Author(s):  
D. O. MARTÍNEZ ◽  
S. CHEN ◽  
G. D. DOOLEN ◽  
R. H. KRAICHNAN ◽  
L.-P. WANG ◽  
...  
Keyword(s):  
Energy Spectrum ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Fluid Turbulence ◽  
Theoretical Predictions ◽  
Dissipation Range ◽  
Good Agreement

High-resolution, direct numerical simulations of three-dimensional incompressible Navier–Stokes equations are carried out to study the energy spectrum in the dissipation range. An energy spectrum of the form A(k/kd)α exp[−βk/kd] is confirmed. The possible values of the parameters α and β, as well as their dependence on Reynolds numbers and length scales, are investigated, showing good agreement with recent theoretical predictions. A ‘bottleneck’-type effect is reported at k/kd≈4, exhibiting a possible transition from near-dissipation to far-dissipation.

Experimental Techniques for Bearing Impedance Measurement

1991 ◽  
Vol 113 (3) ◽  
pp. 335-342 ◽  
Author(s):  
M. J. Goodwin
Keyword(s):  
Experimental Measurement ◽  
Computer Software ◽  
Impedance Measurement ◽  
Experimental Techniques ◽  
Design Stage ◽  
Theoretical Treatment ◽  
Yield Coefficient ◽  
Experimental Procedure ◽  
Advantages And Disadvantages ◽  
Theoretical Predictions

The dynamic characteristics of rotating machinery are almost always influenced by the impedances of the machine bearings (including the bearing supports) and it is particularly important to know of their likely values at the design stage when predicting machine critical speeds, unbalance response, and stability. In many instances the vital data may be obtained from theory which must be confirmed by experimental measurement beforehand, or alternatively the data may be obtained directly from experimental measurement when the appropriate bearing has already been manufactured. The experimental techniques available for use in the measurement of bearing impedances are varied, both in their experimental procedure and in the theoretical treatment of the data that is gathered. The aim of this paper is to provide a concise account of these techniques, and to discuss the potential advantages and disadvantages of each approach. In this document, the procedures described are classified in terms of the type of experimental measuring equipment required. These vary from the simplest of test rigs, which provide only a static load in one direction and where impedances can be evaluated by hand calculation, to sophisticated apparatus capable of providing static and dynamic loads in several directions and which require computer software to extract the bearing impedances from the measured data. The type of experimental procedure selected by the rotor dynamicist will depend upon the experimental facilities available, on the time available to carry out the testing, and on the required reliability of results. Each of these considerations is discussed for each procedure described. It is concluded that measurements made using multifrequency test signals provide more reliable data, although all measurement methods yield coefficient values which agree with theoretical predictions to within about 20 percent in general, and all methods have a significant scatter of results associated with their use.

Modeling of Tool Forces for Worn Tools: Flank Wear Effects

1996 ◽  
Vol 118 (3) ◽  
pp. 359-366 ◽  
Author(s):  
S. Elanayar ◽  
Y. C. Shin
Keyword(s):  
Flank Wear ◽  
General Procedure ◽  
Three Dimensional ◽  
Shear Plane ◽  
Workpiece Material ◽  
Ceramic Tools ◽  
Indentation Force ◽  
Normal Forces ◽  
Theoretical Predictions ◽  
Good Agreement

A general procedure for the separation of ploughing forces from shearing forces on the shear plane is outlined. The first part of the paper deals with the experimental separation of these forces using the predictive machining theory developed by Oxley. The forces are decomposed by first separating the shear forces from the total forces and then employing an iterative procedure to calculate the normal forces on the shear plane. All analysis is conducted for three dimensional cutting. The second part of the paper develops a procedure to model the ploughing forces by accounting for the change in geometry with flank wear. The procedure uses the indentation models along with values of tool and workpiece material constants to determine the indentation force. Models for the indentation depth are developed from a few designed experiments and the predictions by the established models are then compared with experimental results obtained for different cutting conditions. The theoretical predictions of the ploughing forces agree closely with results of the experiments. Additional analysis using ceramic tools also show reasonably good agreement between predictions and experimental measurements.

Coexistence of Multiple Attractors and Crisis Route to Chaos in a Novel Chaotic Jerk Circuit

2016 ◽  
Vol 26 (05) ◽  
pp. 1650081 ◽  
Author(s):  
J. Kengne ◽  
Z. T. Njitacke ◽  
A. Nguomkam Negou ◽  
M. Fouodji Tsostop ◽  
H. B. Fotsin
Keyword(s):  
Equilibrium Points ◽  
Three Dimensional ◽  
Period Doubling ◽  
Chaotic Oscillations ◽  
Multiple Attractors ◽  
Coexistence Of Multiple Attractors ◽  
Theoretical Predictions ◽  
Route To Chaos ◽  
Model Equations ◽  
Good Agreement

In this paper, a novel autonomous RC chaotic jerk circuit is introduced and the corresponding dynamics is systematically investigated. The circuit consists of opamps, resistors, capacitors and a pair of semiconductor diodes connected in anti-parallel to synthesize the nonlinear component necessary for chaotic oscillations. The model is described by a continuous time three-dimensional autonomous system with hyperbolic sine nonlinearity, and may be viewed as a linear transformation of model MO15 previously introduced in [Sprott, 2010]. The structure of the equilibrium points and the discrete symmetries of the model equations are discussed. The bifurcation analysis indicates that chaos arises via the usual paths of period-doubling and symmetry restoring crisis. One of the key contributions of this work is the finding of a region in the parameter space in which the proposed (“elegant”) jerk circuit exhibits the unusual and striking feature of multiple attractors (i.e. coexistence of four disconnected periodic and chaotic attractors). Laboratory experimental results are in good agreement with the theoretical predictions.

scholarly journals Models of inhomogeneous polarization of ferroelectrics and their practical application

2020 ◽  
Vol 10 (01n02) ◽  
pp. 2060015
Author(s):  
Alexander Skaliukh
Keyword(s):  
Experimental Data ◽  
Numerical Experiments ◽  
Constitutive Relations ◽  
Three Dimensional ◽  
Polarization Vector ◽  
Energy Costs ◽  
Polarization Process ◽  
Practical Application ◽  
Real Polarization ◽  
Good Agreement

A three-dimensional mathematical model is proposed that describes the ferroelectric response of polycrystalline ferroelectrics to an electric field in the absence of mechanical stresses. It is based on the separation of the switching process into two related parts: the rotation of the spontaneous polarization vectors and the destruction of the domain wall fixing mechanisms. For each of the parts, the energy costs are calculated, which are the components of the energy balance in the real polarization process. The constitutive relations for the induced and residual components of the polarization vector of the representative volume are obtained. A number of numerical experiments were performed, which showed good agreement with the experimental data.

Pressure Measurements on Flapped Hydrofoils in Cavity Flows and Wake Flows

1967 ◽  
Vol 11 (03) ◽  
pp. 170-189
Author(s):  
M. C. Meijer
Keyword(s):  
Wall Effect ◽  
Cavity Flows ◽  
Pressure Measurements ◽  
Viscous Effect ◽  
Tunnel Wall ◽  
Experimental Procedure ◽  
Wake Flows ◽  
Theoretical Predictions ◽  
Theory And Experiments ◽  
Good Agreement

The purpose of the present experiments is to obtain detailed information about the flow field, such as the pressure distribution, at the surface of a flapped hydrofoil in full cavity or wake flows. The model and the experimental procedure are described. The experimental results obtained have been used to compare with the theoretical predictions, to investigate the tunnel wall effect and to estimate the viscous effect at a sharp corner. Anempirical method for correcting the tunnel wall effect is developed here, the validity of which is supported by tests with models of three different sizes. An appreciable Viscous effect has been found near the hinge of a deflected flap. Except for this effect, the theory and experiments are found to be in good agreement.

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