Thermal Mixing Downstream of a 90-Degree T-Junction: Laminar and Turbulent Flows

2019 ◽  
Author(s):  
Bakhtier Farouk
Keyword(s):  
Turbulent Flows ◽  
Thermophysical Properties ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Inlet Temperature ◽  
Horizontal Pipe ◽  
Thermal Mixing ◽  
Large Eddy ◽  
Inlet Conditions

Abstract A three-dimensional time dependent computational fluid dynamic (CFD) study of laminar and turbulent thermal mixing of two flows entering a 90° T-junction pipe is presented. The two incoming flows (both liquids) in the T-junction enter the flow domain with different inlet velocities, and temperatures. Water flow is considered in both the horizontal pipe and the vertical pipe. Inlet temperature differences and temperature dependent thermophysical properties are considered. Large eddy simulations (LES) with sub-grid scale (SGS) modeling were considered for the simulation of the turbulent cases. The flow characteristics, and thermal mixing behaviors and detailed mixing structures were simulated, and they showed that thermal mixing of the two streams are closely affected by the inlet conditions of the two streams and the inlet thermophysical properties of the two streams.

The Effect of Upstream Flow Conditions to Laminar Mixing in a Miniature Combustion Chamber

2003 ◽  
Author(s):  
Peter L. Woodfield ◽  
Kazuya Tatsumi ◽  
Kazuyoshi Nakabe ◽  
Kenjiro Suzuki
Keyword(s):  
Combustion Chamber ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Baffle Plate ◽  
Micro Gas Turbine ◽  
Laminar Mixing ◽  
Fuel Jet ◽  
Single Jet ◽  
Inlet Conditions ◽  
Volume Method

A three-dimensional unstructured finite-volume method is used to investigate laminar flow characteristics of a miniature chamber with a possible application to micro gas turbine combustor design. The chamber is cylindrical in shape and 20mm in diameter with the fuel stream entering via a single jet in the center of one end of the can. Oxidizer jets are generated by a circular baffle plate having six holes surrounding the fuel jet. Attention is given to the effect of the inlet conditions on the flow structure and mixing pattern inside the chamber. Computations are carried out with the calculation domain inlet being positioned at two different locations; (1) at the immediate entrance to the combustion chamber (2) one combustor diameter upstream of the baffle plate. Numerous inlet conditions are considered including ‘top-hat’, fully-developed, swirling, an annular backward facing step and some asymmetrically skewed profiles. The baffle plate is shown to have a significant smoothing effect on the inlet conditions for a Reynolds number of 100.

Helium Turboexpander for Cryogenic Refrigeration and Liquefaction Cycles: Transient Analysis of Rotor–Stator Interaction

2016 ◽  
Author(s):  
Ashish Alex Sam ◽  
Parthasarathi Ghosh
Keyword(s):  
Turbulent Flows ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Space Length ◽  
Turbine Wheel ◽  
Mechanical Constraints ◽  
Computational Fluid Dynamics Analysis ◽  
Flow Mechanisms ◽  
Rotor Stator Interaction

Computational fluid dynamics analysis of the complex flows in a cryogenic turboexpander is essential for any improvement in its performance. This includes a detailed analysis of the unsteady turbulent flows imparted mainly by the rotor stator interactions. The flow unsteadiness due to rotor stator interaction is caused by the relative motion between the stationary and rotating component, interaction of the turbine wheel blades with the wakes and vortices generated by the upstream blades and at trailing edges. In order to minimize the loss generation due to this unsteadiness, the vaneless space length at the nozzle-turbine wheel interface and the length of the straightening portion at the turbine wheel-diffuser interface should be optimised considering the mechanical constraints. In this paper three dimensional unsteady viscous flow analysis of a helium cryogenic turboexpander was carried out using Ansys CFX to investigate the origin and flow mechanisms that cause these unsteady phenomena. The analysis has been done for three different lengths of straightening duct at the turbine wheel diffuser interface. The performance parameters from the computational results were compared and analysed to understand the flow characteristics in each case.

Aerothermal Study of the Unsteady Flow Field in a Transonic Gas Turbine With Inlet Temperature Distortions

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
S. Salvadori ◽  
F. Montomoli ◽  
F. Martelli ◽  
P. Adami ◽  
K. S. Chana ◽  
...  
Keyword(s):  
Rotor Blade ◽  
Numerical Study ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Inlet Temperature ◽  
Phase Lag ◽  
Turbine Stage ◽  
Inlet Conditions ◽  
University Of Florence ◽  
The University

Computational fluid dynamics (CFD) prediction of the unsteady aerothermal interaction in the HP turbine stage, with inlet temperature nonuniformity, requires appropriate unsteady modeling and a low diffusive numerical scheme coupled with suitable turbulence models. This maybe referred to as high fidelity CFD. A numerical study has been conducted by the University of Florence in collaboration with ONERA to compare capabilities and limitations of their CFD codes for such flows. The test vehicle used for the investigation is a turbine stage of three-dimensional design from the QinetiQ turbine facility known as MT1. This stage is a high pressure transonic stage that has an unshrouded rotor, configured, and uncooled with 32 stators and 60 rotor blades. Two different CFD solvers are compared that use different unsteady treatments of the interaction. A reduced count ratio technique has been used by the University of Florence with its code HYBFLOW, while a phase lag model has been used by ONERA in their code, ELSA. Four different inlet conditions have been simulated and compared with focus on the experimental values provided by QinetiQ in the frame of TATEF and TATEF2 EU Sixth Framework Projects. The differences in terms of performance parameters and hot fluid redistribution, as well as the time- and pitch-averaged radial distributions on a plane downstream of the rotor blade, have been underlined. Special attention was given to the predictions of rotor blade unsteady pressure and heat transfer rates.

scholarly journals Large-eddy Simulation of Wall-bounded Turbulent Flow with High-order Discrete Unified Gas-Kinetic Scheme

2020 ◽  
Author(s):  
Rui Zhang ◽  
Chengwen Zhong ◽  
Sha Liu ◽  
Congshan Zhuo
Keyword(s):  
Turbulent Flows ◽  
Parallel Implementation ◽  
Computational Cost ◽  
Three Dimensional ◽  
Kinetic Scheme ◽  
Equilibrium Distribution Function ◽  
Third Order ◽  
Two Stage ◽  
Large Eddy ◽  
Unified Gas Kinetic Scheme

Abstract In this paper, we introduce the incompressible discrete Maxwellian equilibrium distribution function and external forces into the two-stage third-order Discrete Unified Gas-Kinetic Scheme (DUGKS) for simulating low-speed incompressible turbulent flows with forcing term. The Wall-Adapting Local Eddy-viscosity (WALE) and Vreman sub-grid models for Large-Eddy Simulations (LES) of wall-bounded turbulent flows are coupled within the present framework. In order to simulate the three-dimensional turbulent flows associated with great computational cost, a parallel implementation strategy for the present framework is developed, and is validated by three canonical wall-bounded turbulent flows, viz., the fully developed turbulent channel flow at a friction Reynolds number (Re) about 180, the turbulent plane Couette flow at a friction Re number about 93 and three-dimensional lid-driven cubical cavity flow at a Re number of 12000. The turbulence statistics are computed by the present approach with both WALE and Vreman models, and their predictions match precisely with each other. Especially, the predicted flow physics of three-dimensional lid-driven cavity are consistent with the description from abundant literatures. While, they have small discrepancies in comparison to the Direct Numerical Simulation (DNS) due to the relatively low grid resolution. The present numerical results verify that the present two-stage third-order DUGKS-based LES method is capable for simulating inhomogeneous wall-bounded turbulent flows and getting reliable results with relatively coarse grids.

Fluid Dynamic Study in a Femoral Artery Branch Casting of Man With Upstream Main Lumen Curvature for Steady Flow

1985 ◽  
Vol 107 (3) ◽  
pp. 240-248 ◽  
Author(s):  
M. R. Back ◽  
Y. I. Cho ◽  
L. H. Back
Keyword(s):  
Steady Flow ◽  
Fluid Transport ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Pressure Distributions ◽  
Flow Investigation ◽  
Measured Pressure

An in-vitro, steady flow investigation was conducted in a hollow, transparent vascular replica of the profunda femoris branch of man for a range of physiological flow conditions. The replica casting tested was obtained from a human cadaver and indicated some plaque formation along the main lumen and branch. The flow visualization observations and measured pressure distributions indicated the highly three-dimensional flow characteristics with arterial curvature and branching, and the important role of centrifugal effects in fluid transport mechanisms.

NUMERICAL SIMULATION OF THE EFFECT OF INITIAL NONUNIFORMITY AND FLUCTUATIONS OF FUEL CONCENTRATION ON COMBUSTION STABILITY AND NOX AND CO EMISSION IN A LEAN PREMIXED METHANE/AIR COMBUSTOR

2020 ◽  
Author(s):  
K. Ya. Yakubovskiy ◽  
◽  
A. B. Lebedev ◽  
P. D. Toktaliev ◽  
◽  
...  
Keyword(s):  
Combustion Chamber ◽  
Turbulent Flows ◽  
Three Dimensional ◽  
Combustion Stability ◽  
Fuel Concentration ◽  
Eddy Simulation ◽  
Flow Parameters ◽  
Low Emission ◽  
Large Eddy ◽  
Co Emission

The effect of initial nonuniformity and fluctuations of fuel concentration on the combustion stability and NOx and CO emission in the model combustion chamber was analyzed with the use of previously developed simple and computationally inexpensive Large Eddy Simulation (LES) methodology for simulation of three-dimensional unsteady turbulent flows with premixed combustion of methane-air mixture in low-emission combustion chamber which geometry is represented by channel with the backward facing step. Typical sizes of the combustion chamber, flow parameters, turbulence level, and method of flame front stabilization are close to those of full-sized industrial combustors.

Aero-Thermal Study of the Unsteady Flow Field in a Transonic Gas Turbine With Inlet Temperature Distortions

2008 ◽  
Author(s):  
Francesco Martelli ◽  
Paolo Adami ◽  
Simone Salvadori ◽  
Kam S. Chana ◽  
Lionel Castillon
Keyword(s):  
Rotor Blade ◽  
Numerical Study ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Inlet Temperature ◽  
Phase Lag ◽  
Turbine Stage ◽  
Inlet Conditions ◽  
University Of Florence ◽  
The University

CFD prediction of the unsteady aero-thermal interaction in the HP turbine stage, with inlet temperature non-uniformity, requires appropriate unsteady modelling and a low diffusive numerical scheme coupled with suitable turbulence models. This maybe referred to as high fidelity CFD. A numerical study has been conducted by the University of Florence in collaboration with ONERA to compare capabilities and limitations of their CFD codes for such flows. The test vehicle used for the investigation is a turbine stage of three-dimensional design from the QinetiQ turbine facility known as MT1. This stage is a high pressure (HP) transonic stage that has an un-shrouded rotor, configured un-cooled with 32 stators and 60 rotor blades. Two different CFD solvers are compared that use different unsteady treatment of the interaction. A reduced count ratio technique has been used by the University of Florence with its code HybFlow, while a phase lag model has been used by ONERA in their code, elsA. Four different inlet conditions have been simulated and compared with a focus on the experimental values provided by QinetiQ in the frame of TATEF and TATEF2 EU 6th Framework projects. The differences in terms of performance parameters and hot fluid redistribution, as well as the time- and pitch-averaged radial distributions on a plane downstream of the rotor blade, have been underlined. Special attention was given to the predictions of rotor blade unsteady pressure and heat transfer rates.

Generation of Three-Dimensional Turbulent Inlet Conditions for Large-Eddy Simulation

AIAA Journal ◽  
2004 ◽  
Vol 42 (3) ◽  
pp. 447-456 ◽  
Author(s):  
P. Druault ◽  
S. Lardeau ◽  
J.-P. Bonnet ◽  
F. Coiffet ◽  
J. Delville ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Three Dimensional ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Inlet Conditions
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