Fluid Forces Induced by Vortex Shedding

1976 ◽  
Vol 98 (1) ◽  
pp. 19-24 ◽  
Author(s):  
R. D. Blevins ◽  
T. E. Burton
Keyword(s):  
Experimental Data ◽  
Vortex Shedding ◽  
Model Parameters ◽  
Amplitude Dependence ◽  
Fluid Forces ◽  
At Resonance ◽  
Elastic Cylinders ◽  
Random Vibration Theory ◽  
Semi Empirical ◽  
Good Agreement

A semi-empirical, dynamic model for investigating the fluid forces induced on a bluff cylinder by vortex shedding is developed using random vibration theory. The model includes both spanwise correlation effects and the amplitude dependence of the correlated vortex forces. Model parameters are determined by experimental data. The results are then applied to determine the forces exerted on elastic cylinders at resonance with vortex shedding. The predictions are in good agreement with experimental data.

A Hybrid Semi-empirical Model for Lean Blow-Out Limit Predictions of Aero-engine Combustors

2014 ◽  
Vol 137 (3) ◽  
Author(s):  
Bin Hu ◽  
Yong Huang ◽  
Jianzhong Xu
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Empirical Model ◽  
The Other ◽  
Model Parameters ◽  
Model Parameter ◽  
Other Hand ◽  
Aero Engine ◽  
Semi Empirical

According to the Lefebvre's model and flame volume (FV) concept, an FV model about lean blow-out (LBO) was proposed by authors in early study. On the other hand, due to the model parameter (FV) contained in FV model is obtained based on the experimental data, FV model could only be used in LBO analysis instead of prediction. In view of this, a hybrid FV model is proposed that combines the FV model with numerical simulation in the present study. The model parameters contained in the FV model are all estimated from the simulated nonreacting flows. Comparing with the experimental data for 11 combustors, the maximum and average uncertainties of hybrid FV model are ±16% and ±10%.

scholarly journals Validation of NEPTUNE-CFD Two-Phase Flow Models Using Experimental Data

2014 ◽  
Vol 2014 ◽  
pp. 1-19 ◽  
Author(s):  
Jorge Pérez Mañes ◽  
Victor Hugo Sánchez Espinoza ◽  
Sergio Chiva Vicent ◽  
Michael Böttcher ◽  
Robert Stieglitz
Keyword(s):  
Experimental Data ◽  
Void Fraction ◽  
Two Phase Flow ◽  
Model Parameters ◽  
Phase Flow ◽  
Cfd Model ◽  
Two Phase ◽  
Flow Models ◽  
Phase Models ◽  
Good Agreement

This paper deals with the validation of the two-phase flow models of the CFD code NEPTUNEC-CFD using experimental data provided by the OECD BWR BFBT and PSBT Benchmark. Since the two-phase models of CFD codes are extensively being improved, the validation is a key step for the acceptability of such codes. The validation work is performed in the frame of the European NURISP Project and it was focused on the steady state and transient void fraction tests. The influence of different NEPTUNE-CFD model parameters on the void fraction prediction is investigated and discussed in detail. Due to the coupling of heat conduction solver SYRTHES with NEPTUNE-CFD, the description of the coupled fluid dynamics and heat transfer between the fuel rod and the fluid is improved significantly. The averaged void fraction predicted by NEPTUNE-CFD for selected PSBT and BFBT tests is in good agreement with the experimental data. Finally, areas for future improvements of the NEPTUNE-CFD code were identified, too.

Regression models to predict herbage production and digestibility in a non-regular sequence of cuts

1979 ◽  
Vol 92 (3) ◽  
pp. 575-585 ◽  
Author(s):  
P. R. Edelsten ◽  
A. J. Corrall
Keyword(s):  
Experimental Data ◽  
Regression Models ◽  
Regular Sequence ◽  
Model Parameters ◽  
Yield Model ◽  
Cutting Interval ◽  
Time Of Year ◽  
Cutting Experiments ◽  
Cutting Strategy ◽  
Good Agreement

SUMMARYRegression models were constructed to predict the yields and digestibilities of herbage cut in different sequences of harvests.The yield model used a seasonal production curve modified by the effects of defoliation. Values for the model parameters were obtained by fitting the model to experimental data using a non-linear regression procedure. When these parameters were used, to predict treatment effects in another series of experimental data, good agreement was obtained. The digestibility model incorporated the effect on digestibility time of year, regrowth time and yield.Using the models to interpolate between the results of cutting experiments, annual yields were shown to increase with the date of first cut and also with the interval between subsequent cuts, whereas the average digestibility of the harvested material ecreased with the date of first cut and with the subsequent cutting interval. Finally, a procedure was devised for combining the two models in order to find an optimum cutting strategy for a hypothetical animal production system.

Hydrodynamics of the Flow Around a Circular Cylinder Sheathed by a Porous Layer

2004 ◽  
Author(s):  
M. P. Sobera ◽  
C. R. Kleijn ◽  
P. Brasser ◽  
H. E. A. van den Akker
Keyword(s):  
Experimental Data ◽  
Circular Cylinder ◽  
Porous Layer ◽  
Vortex Shedding ◽  
Small Distance ◽  
Grid Refinement ◽  
Solid Cylinder ◽  
Local Grid Refinement ◽  
Local Grid ◽  
Good Agreement

A detailed study of the turbulent flow at Re = 3900 around a circular cylinder, sheathed at some small distance by a porous layer, has been performed by means of Direct Numerical Simulation with a commercial unstructured finite volume based Computational Fluid Dynamics solver. First, to benchmark the performance of this code and the validity of the applied local grid refinement, simulations of the flow around a bare circular cylinder at the same Re were performed. Results were compared to that of an academic CFD solver and to numerical and experimental data from literature and good agreement was found. Subsequently, a detailed study of the flow around a porous layer sheathed cylinder at the same Re, was performed. The flow in the space between the outer porous and the inner solid cylinder was found to be laminar and periodic, with a frequency locked to that of the vortex shedding in the wake behind the cylinder. A good agreement was found to experimental data from literature.

VLE Determination of Carbon Dioxide Loaded Aqueous Alkanolamine Mixtures Using Modified Kent Eisenberg Model

2017 ◽  
Vol 231 (11-12) ◽  
Author(s):  
Humbul Suleman ◽  
Abdulhalim Shah Maulud ◽  
Zakaria Man
Keyword(s):  
Experimental Data ◽  
Carbon Dioxide ◽  
Model Parameters ◽  
Thermodynamic Models ◽  
Carbon Dioxide Absorption ◽  
Proposed Model ◽  
Wide Range ◽  
Experimental Values ◽  
Good Agreement

AbstractA computationally simple thermodynamic framework has been presented to correlate the vapour-liquid equilibria of carbon dioxide absorption in five representative types of alkanolamine mixtures. The proposed model is an extension of modified Kent Eisenberg model for the carbon dioxide loaded aqueous alkanolamine mixtures. The model parameters are regressed on a large experimental data pool of carbon dioxide solubility in aqueous alkanolamine mixtures. The model is applicable to a wide range of temperature (298–393 K), pressure (0.1–6000 kPa) and alkanolamine concentration (0.3–5 M). The correlated results are compared to the experimental values and found to be in good agreement with the average deviations ranging between 6% and 20%. The model results are comparable to other thermodynamic models.

Acoustic Resonance in Heat Exchanger Tube Bundles—Part II: Prediction and Suppression of Resonance

1987 ◽  
Vol 109 (3) ◽  
pp. 282-288 ◽  
Author(s):  
R. D. Blevins ◽  
M. M. Bressler
Keyword(s):  
Experimental Data ◽  
Heat Exchanger ◽  
Vortex Shedding ◽  
Empirical Model ◽  
Acoustic Resonance ◽  
Heat Exchanger Tube ◽  
Tube Bundles ◽  
Semi Empirical ◽  
Exchanger Tube

In the first part of this series, experimental data were presented which suggest that the acoustic resonance in heat exchanger tube bundles is tied to periodic vortex shedding from the tubes. In this paper, a semi-empirical model for predicting the onset of resonance is developed. This model is compared with experimental data and other models from the literature. Methods of suppressing the resonance are developed and experimental data on their effectiveness are presented.

Temperature dependence of dielectric properties of moist soils

2008 ◽  
Vol 45 (6) ◽  
pp. 888-894 ◽  
Author(s):  
Arun P. Jaganathan ◽  
Erez N. Allouche
Keyword(s):  
Experimental Data ◽  
Dielectric Properties ◽  
Land Mines ◽  
Temperature Dependency ◽  
Moisture Contents ◽  
Moist Sand ◽  
Proposed Model ◽  
Dielectric Model ◽  
Semi Empirical ◽  
Good Agreement

Heating of soil using microwaves has several applications in geosciences, including soil remediation, neutralization of land mines, and microwave-enhanced thermography. Numerical simulation of microwave-induced soil heating processes requires knowledge of the electrical properties of the soil as a function of temperature, moisture content, and frequency of the electromagnetic wave. This paper describes a semi-empirical model for calculating the dielectric properties of moist soils at various moisture contents, temperatures, and frequencies (within the band of 1–10 GHz). The proposed model is an extension of the generalized refractive mixing dielectric model (GRMDM) for moist soils. Predictions of the proposed model were found to be in good agreement with experimental data reported in the literature. Results of a parametric study suggest that the temperature dependency of the dielectric properties of moist sand is more pronounced for higher volumetric moisture contents.

A Model for Vortex Induced Oscillation of Structures

1974 ◽  
Vol 41 (3) ◽  
pp. 581-586 ◽  
Author(s):  
W. D. Iwan ◽  
R. D. Blevins
Keyword(s):  
Experimental Data ◽  
Circular Cylinder ◽  
Analytical Model ◽  
Vortex Shedding ◽  
Fluid Dynamic ◽  
Model Parameters ◽  
Structural Systems ◽  
Dynamic Effects ◽  
Hidden Variable ◽  
Model Predictions

A model is presented for the analysis of the response of structural systems excited by vortex shedding. The model is based on the introduction of a hidden variable to describe the fluid dynamic effects. Model parameters may be determined from experimental data for fixed and forced elements and the model used to predict the response of elastically mounted elements. Analytical model predictions are compared with experimental results for a circular cylinder.

scholarly journals Estimation of viscosity for some silicate ternary slags

2014 ◽  
Vol 50 (2) ◽  
pp. 139-144 ◽  
Author(s):  
Q. Shu ◽  
L. Wang ◽  
K.C. Chou
Keyword(s):  
Experimental Data ◽  
General Solution ◽  
Gibbs Energy ◽  
Binary Systems ◽  
Geometrical Model ◽  
Solution Model ◽  
Mean Deviation ◽  
Model Parameters ◽  
General Solution Model ◽  
Good Agreement

A new method, combining KTH model with geometrical model (General solution model by Chou) to estimate viscosity of some ternary silicate slags, was proposed in this work. According to modified KTH model, viscous Gibbs free energy for mixing of ternary slags was estimated by employing general solution model. It was found that viscous Gibbs energy for mixing of ternary system could be calculated using solely viscous Gibbs energy for mixing of sub-binary systems. The viscosities of five ternary slags CaO-MnO-SiO2, CaO-FeO-SiO2, FeO-MnO-SiO2, CaO-MgO-SiO2 and FeO-MgO-SiO2 were estimated in the present work. A good agreement with available experimental data, with mean deviation less than 20%, was achieved. The modified KTH model has advantages with less model parameters and improved estimation ability by comparison to original KTH model.

α-Decay half-lives of even–even nuclei of Pb, Po, Rn and Ra isotopes

2019 ◽  
Vol 28 (03) ◽  
pp. 1950017 ◽  
Author(s):  
S. S. Hosseini ◽  
H. Hassanabadi ◽  
Dashty T. Akrawy
Keyword(s):  
Experimental Data ◽  
Potential Barrier ◽  
Ground State ◽  
Α Decay ◽  
Model Based ◽  
Semi Empirical ◽  
Good Agreement

In the present work, we intended to study the [Formula: see text]-decay half-lives of the even–even nuclei from [Formula: see text]Po to [Formula: see text]Ra in ground state. We investigated a semi-empirical, one-parameter model based on tunneling through a potential barrier with the centrifugal and overlapping effects. Half-lives of [Formula: see text]-decay of even–even nuclei calculated by using different versions of proximity potentials (gpp77, MCW76 and MB77) are compared to experimental data. Also, the computed half-lives are compared with the Royer formula, Akrawy and Poenaru (AKRE) formula, modify Ren (MRen B) formula and Denisov–Khudenko (DEKH) formula and with the experimental data. The results are in good agreement with the experimental data.

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