Comparison of an integral model for predicting the dispersion of a turbulent jet in a crossflow with experimental data

1990 ◽  
Vol 3 (2) ◽  
pp. 264
Keyword(s):  
Experimental Data ◽  
Turbulent Jet ◽  
Integral Model

scholarly journals A theoretical model of a wake of a body towed in a stratified fluid at large Reynolds and Froude numbers

2006 ◽  
Vol 13 (3) ◽  
pp. 247-253 ◽  
Author(s):  
Y. I. Troitskaya ◽  
O. A. Druzhinin ◽  
D. A. Sergeev ◽  
V. V. Papko ◽  
G. N. Balandina
Keyword(s):  
Experimental Data ◽  
Theoretical Model ◽  
Momentum Transfer ◽  
Hydrodynamic Instability ◽  
Jet Flow ◽  
Stratified Fluid ◽  
Turbulent Jet ◽  
Wake Flow ◽  
Mean Flow ◽  
Turbulent Jet Flow

Abstract. The objective of the present paper is to develop a theoretical model describing the evolution of a turbulent wake behind a towed sphere in a stably stratified fluid at large Froude and Reynolds numbers. The wake flow is considered as a quasi two-dimensional (2-D) turbulent jet flow whose dynamics is governed by the momentum transfer from the mean flow to a quasi-2-D sinuous mode growing due to hydrodynamic instability. The model employs a quasi-linear approximation to describe this momentum transfer. The model scaling coefficients are defined with the use of available experimental data, and the performance of the model is verified by comparison with the results of a direct numerical simulation of a 2-D turbulent jet flow. The model prediction for the temporal development of the wake axis mean velocity is found to be in good agreement with the experimental data obtained by Spedding (1997).

Experiments and modeling of a dual-mode, turbulent jet ignition engine

2019 ◽  
Vol 21 (6) ◽  
pp. 966-986 ◽  
Author(s):  
Sedigheh Tolou ◽  
Harold Schock
Keyword(s):  
Experimental Data ◽  
Thermal Efficiency ◽  
Internal Combustion Engines ◽  
Peak Pressure ◽  
Operating Conditions ◽  
Turbulent Jet ◽  
Engine Fuel ◽  
Main Chamber ◽  
Dual Mode ◽  
Ignition System

The dual-mode, turbulent jet ignition system is a promising combustion technology to achieve high diesel-like thermal efficiency at medium to high loads and potentially exceed diesel efficiency at low-load operating conditions. The dual-mode, turbulent jet ignition systems to date proved a high level of improvement in thermal efficiency compared to conventional internal combustion engines. However, some questions were still unanswered. The most frequent question regarded power requirements for delivering air to the pre-chamber of a dual-mode, turbulent jet ignition system. In addition, there was no study available to predict the expected efficiency of a dual-mode, turbulent jet ignition engine in a multi-cylinder configuration. This study, for the first time, predicts the ancillary work requirement to operate the dual-mode, turbulent jet ignition system. It also presents a novel, reduced order, and physics-based model of the dual-mode, turbulent jet ignition engine with a pre-chamber valve assembly. The developed model was calibrated based on experimental data from the Prototype II dual-mode, turbulent jet ignition engine. The simulation results were in good agreement with the experimental data. The validity of the model was observed based on the standard metric of the coefficient of determination as well as comparison plots for in-cylinder pressures. Numerical predictions were compared to experiments for three metrics of main chamber combustion: gross indicated mean effective pressure, main chamber peak pressure, and main chamber phasing for the peak pressure. Predictions were within 5% of experimental data, with one exception of 6%. In addition, the absolute root mean square errors of in-cylinder pressures for both pre- and main-combustion chambers were below 0.35. The calibrated model was further studied to introduce a predictive and generalized model for dual-mode, turbulent jet ignition engines. Such a model can project engine behavior in a multi-cylinder configuration over the entire engine fuel map.

Simulation of Methanol-Air Two-Phase Flames Using Various Turbulent Combustion Models

2009 ◽  
Author(s):  
F. Wang ◽  
Y. Huang ◽  
Y. Z. Wu
Keyword(s):  
Experimental Data ◽  
Turbulent Combustion ◽  
Turbulent Jet ◽  
Combustion Model ◽  
Air Flow Rate ◽  
Two Phase ◽  
Jet Flame ◽  
Combustion Simulation ◽  
Turbulent Combustion Model ◽  
Turbulent Models

Though fossil fuel is running out, liquid fuels nowadays still provide the most energy used by industrial furnaces, automotive and aero engines. How to predict a two-phase turbulent combustion flame is still a big problem to designers. Generally, the liquid fuel is sprayed and mixed with oxygen, and the flame characteristics depends on the fuel atomization, the fuel droplet spatial distribution, and its interaction with the turbulent oxidizer flow field: turbulent heat, mass and momentum transfer, complicated chemical kinetics, and turbulent-chemistry interaction. Turbulent combustion model is a key point for the two phase combustion simulation. For its short time consuming, Reynolds Averaged Navier Stokes (RANS) method nowadays still is the major tool for gas turbine chamber (GTC) designers, but there is not a universal method in RANS GTC spray combustion simulation at present especially for the two-phase turbulent combustion. The Eddy-Break-Up turbulent combustion model (EBU), Eddy Dissipation Concept turbulent combustion model (EDC), steady Laminar Flame-let turbulent combustion Model (LFM) and the Composition PDF transport turbulent combustion model (CPDF) are all widely used models. In this paper, these four turbulent models are used to simulate a methane-air turbulent jet flame measured by Sandia Lab first, then three methanol-air two-phase turbulent flames, in order to know the ability of these turbulent models. In the gas turbulent jet flame simulation, the result of LFM model and CPDF model are in better agreement with the experimental data than those of the EBU and the EDC models’ results. The reason is that the EBU model and EDC model are overestimated the effect of turbulent. In the three different cases of the two phase combustion simulation, CPDF is the best. The prediction ability of the other three models is different in different cases. The EDC predictions are closer to the experimental data when the air flow rate value is lower, whereas the LFM predictions are better when the air flow rate value is higher.

Bingham Fluid Flow in the Entrance Region of a Pipe

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
Basma Baioumy ◽  
Rachid Chebbi ◽  
Nabil Abdel Jabbar
Keyword(s):  
Experimental Data ◽  
Boundary Layer ◽  
Fluid Flow ◽  
Pressure Drop ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Bingham Fluid ◽  
Entrance Region ◽  
Integral Model ◽  
Fully Developed Flow

Abstract Laminar Bingham fluid flow in the entrance region of a circular pipe is investigated using a momentum integral model. The fully developed flow is uniform in the core region, while the velocity changes in the annular part of the cross section of the pipe. The inlet-filled region concept is adopted. In the inlet region, the boundary layer thickness increases until the size of the plug flow area reaches the fully developed flow size. The model converges to the fully developed solution in the filled region. The model provides the velocity, pressure drop, and skin friction coefficient profiles. The pressure drop results are in good agreement with published experimental data. The flow results asymptotically converge to the fully developed values. In addition, the results are consistent with published Newtonian fluid flow experimental data and theoretical results for the boundary layer thickness, pressure drop, and centerline velocity for small values of the Bingham number.

Analysis of Coupled CFD-DEM Simulations in Dense Particle-Laden Turbulent Jet Flow

2020 ◽  
Author(s):  
Dustin Weaver ◽  
Sanja Miskovic
Keyword(s):  
Experimental Data ◽  
Particle Flux ◽  
Axial Direction ◽  
Jet Flow ◽  
Turbulent Jet ◽  
Sufficient Information ◽  
Dense Particle ◽  
Dem Simulations ◽  
Mesh Resolution ◽  
Turbulent Jet Flow

Abstract In this paper, coupled CFD-DEM simulations of dense particle-laden jet flow are performed using CFDEM® coupling interface that couples LAMMPS-based LIGGGHTS® DEM engine with OpenFOAM CFD framework. Suspensions of mono-sized spherical glass particles with 80 microns diameter and a mass loading of 0.23 and 0.86 are considered. Three different CFD meshes are used with an average mesh resolution dimension of 3.06, 2.67, and 1.86 particle diameters and it is determined that mesh resolution does not change results for void fraction calculation (using the divided model) of the CFD-DEM equations. Samples of particle flux are taken at 0.1, 10, and 20 nozzle diameters along the axial direction of the jet region. The numerical results for particle flux are compared with a well cited experimental data found in literature. The CFD-DEM simulations in turbulent jet flow are found to be highly sensitive to initial particle velocity inputs but the experimental data provide sufficient information to produce comparable results.

A vortex-street model of the flow in the similarity region of a two-dimensional free turbulent jet

1982 ◽  
Vol 123 ◽  
pp. 523-535 ◽  
Author(s):  
J. W. Oler ◽  
V. W. Goldschmidt
Keyword(s):  
Experimental Data ◽  
Reynolds Stress ◽  
Turbulent Jet ◽  
Vortex Street ◽  
Two Dimensional ◽  
Mean Flow ◽  
Mean Velocity ◽  
The Core ◽  
The Mean ◽  
Similarity Relationships

The mean-velocity profiles and entrainment rates in the similarity region of a two-dimensional jet are generated by a simple superposition of Rankine vortices arranged to represent a vortex street. The spacings between the vortex centres, their two-dimensional offsets from the centreline, as well as the core radii and circulation strengths, are all governed by similarity relationships and based upon experimental data.Major details of the mean flow field such as the axial and lateral mean-velocity components and the magnitude of the Reynolds stress are properly determined by the model. The sign of the Reynolds stress is, however, not properly predicted.

A Modified Fractional Calculus Approach to Model Hysteresis

2010 ◽  
Vol 77 (3) ◽  
Author(s):  
Mohammed Rabius Sunny ◽  
Rakesh K. Kapania ◽  
Ronald D. Moffitt ◽  
Amitabh Mishra ◽  
Nakhiah Goulbourne
Keyword(s):  
Experimental Data ◽  
Fractional Calculus ◽  
Fractional Derivative ◽  
Fractional Integral ◽  
Conductive Polymer ◽  
Polymer Nanocomposite ◽  
Hysteretic Behavior ◽  
Integral Model ◽  
Strain Variation ◽  
Integer Order

This paper describes the development of a fractional calculus approach to model the hysteretic behavior shown by the variation in electrical resistances with strain in conductive polymers. Experiments have been carried out on a conductive polymer nanocomposite sample to study its resistance-strain variation under strain varying with time in a triangular manner. A combined fractional derivative and integer order integral model and a fractional integral model (with two submodels) have been developed to simulate this behavior. The efficiency of these models has been discussed by comparing the results, obtained using these models, with the experimental data. It has been shown that by using only a few parameters, the hysteretic behavior of such materials can be modeled using the fractional calculus with some modifications.

Equilibrium similarity solution of the turbulent transport equation along the centreline of a round jet

2015 ◽  
Vol 772 ◽  
pp. 740-755 ◽  
Author(s):  
H. Sadeghi ◽  
P. Lavoie ◽  
A. Pollard
Keyword(s):  
Experimental Data ◽  
Kinetic Energy ◽  
Structure Function ◽  
Transport Equation ◽  
Power Law ◽  
Turbulent Jet ◽  
Order Structure ◽  
Current Analysis ◽  
Power Law Decay ◽  
The Mean

A novel similarity-based form is derived of the transport equation for the second-order velocity structure function of$\langle ({\it\delta}q)^{2}\rangle$along the centreline of a round turbulent jet using an equilibrium similarity analysis. This self-similar equation has the advantage of requiring less extensive measurements to calculate the inhomogeneous (decay and production) terms of the transport equation. It is suggested that the normalised third-order structure function can be uniquely determined when the normalised second-order structure function, the power-law exponent of$\langle q^{2}\rangle$and the decay rate constants of$\langle u^{2}\rangle$and$\langle v^{2}\rangle$are available. In addition, the current analysis demonstrates that the assumption of similarity, combined with an inverse relation between the mean velocity$U$and the streamwise distance$x-x_{0}$from the virtual origin (i.e. $U\propto (x-x_{0})^{-1}$), is sufficient to predict a power-law decay for the turbulence kinetic energy ($\langle q^{2}\rangle \propto (x-x_{0})^{m}$), rather than requiring a power-law decay ($m=-2$) as an additionalad hocassumption. On the basis of the current analysis, it is suggested that the mean kinetic energy dissipation rate,$\langle {\it\epsilon}\rangle$, varies as$(x-x_{0})^{m-2}$. These theoretical results are tested against new experimental data obtained along the centreline of a round turbulent jet as well as previously published data on round jets for$11\,000\leqslant \mathit{Re}_{D}\leqslant 184\,000$over the range$10\leqslant x/D\leqslant 90$. For the present experiments,$\langle q^{2}\rangle$exhibits power-law behaviour with$m=-1.83$. The validity of this solution is confirmed using other experimental data where$\langle q^{2}\rangle$follows a power law with$-1.89\leqslant m\leqslant -1.78$. The present similarity form of the transport equation for$\langle ({\it\delta}q)^{2}\rangle$is also shown to be closely satisfied by the experimental data.

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