Application of Viscous Analyses to the Design of Jet Exhaust Powered Lift Installations

1980 ◽  
Vol 102 (3) ◽  
pp. 626-631 ◽  
Author(s):  
E. Tjonneland ◽  
S. F. Birch
Keyword(s):  
Numerical Methods ◽  
Strong Coupling ◽  
Recent Progress ◽  
Three Dimensional ◽  
Numerical Procedure ◽  
Turbulence Models ◽  
External Flow ◽  
Analysis Procedure ◽  
Analysis Tool

The application of available numerical methods to the design of powered lift installations is reviewed. For this application, where strong coupling exists between the jet exhaust and the external flow, a three-dimensional viscous analysis tool is needed. The task of selecting a suitable analysis procedure is first outlined, with particular emphasis on the need for careful coordination of the various elements of the task. Problems and progress in the development of turbulence models are then discussed, and some selected three-dimensional calculations are presented to illustrate recent progress. Finally, a numerical procedure, currently under development for a particular powered lift application, is briefly described.

scholarly journals Quantum chaos for point scatterers on flat tori

2014 ◽  
Vol 372 (2007) ◽  
pp. 20120509 ◽  
Author(s):  
Henrik Ueberschär
Keyword(s):  
Wave Function ◽  
Strong Coupling ◽  
Quantum Chaos ◽  
Recent Progress ◽  
Three Dimensional ◽  
Point Scatterer ◽  
Open Problems ◽  
Survey Article ◽  
Delta Potential ◽  
Flat Tori

This survey article deals with a delta potential—also known as a point scatterer—on flat two- and three-dimensional tori. We introduce the main conjectures regarding the spectral and wave function statistics of this model in the so-called weak and strong coupling regimes. We report on recent progress as well as a number of open problems in this field.

An Analytical/Numerical Procedure for Structural Analysis of Hybrid Riser Systems

2005 ◽  
Author(s):  
G. J. O. Rodrigues ◽  
Daniel C. T. Cardoso ◽  
Beatriz S. L. P. de Lima ◽  
Breno P. Jacob ◽  
Antonio C. Fernandes
Keyword(s):  
Finite Element ◽  
Dynamic Simulation ◽  
Production Systems ◽  
Three Dimensional ◽  
Numerical Procedure ◽  
Solution Procedure ◽  
Analysis Tool ◽  
Full Time ◽  
Transient Effects ◽  
Dimensional Solution

In deep and ultra-deep water petroleum exploitation activities, floating production systems such as semi submersible platforms and FPSO (Floating Production, Storage and Offloading) units have been commonly employed. However, the utilization of flexible risers in ultra-deep waters has been hindered by technical and economical reasons. On the other hand, first order motions from the floating unit due to environmental loads are not favorable to the use of Steel Catenary Risers (SCR) in a free-hanging configuration. This fact has motivated several studies on hybrid riser systems, including the system studied in this work, which is based on a sub-surface buoy with large dimensions, moored to the seabed by tethers. This system employs flexible lines connecting the floating unit to the buoy, in the region where dynamic effects are more relevant due to the floating unit motions, and also SCRs that extend from the buoy to the seabed, in the region where dynamic motions are not so significant. The objective of this work is to describe a solution procedure for the analysis of such a hybrid riser system. This procedure is based on an analytical formulation that is solved numerically. One of the main features of this procedure is the fact that it takes into account the effects of current loads acting on the lines. Current profiles can be considered, with direction and velocities varying with depth, therefore configuring a full three-dimensional solution. This procedure can be employed either as a preliminary static analysis tool, to be used in parametric studies in order to assess the feasibility of candidate configurations of hybrid riser systems, or else for the generation of finite-element meshes for a full time-domain nonlinear dynamic simulation. It is important to start the dynamic simulation from a statically balanced configuration, since the transient effects can be dramatically shortened and the total simulation time can be reduced. The results obtained from this procedure are compared with a discrete solution obtained using a nonlinear finite-element based solver. The strategy considered here is intended to be an approach that will speed up the tasks involved in the design of hybrid risers systems based on the subsurface buoy concept.

scholarly journals INVESTIGATION OF THE GRID MODEL AND TURBULENCE MODEL PARAMETERS INFLUENCE ON QUALITY OF TURBINE ROTOR BLADE TIP CLEARANCE AREA AERODYNAMIC PROCESSES MODELING

2021 ◽  
pp. 67-78
Author(s):  
Diana Popova ◽  
◽  
Denis Popov ◽  
Nikita Samoylenko ◽  
◽  
...  
Keyword(s):  
Mathematical Modeling ◽  
Numerical Methods ◽  
Turbulence Model ◽  
Rotor Blade ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Design Stage ◽  
Model Parameters ◽  
Grid Model

Aerodynamic processes mathematical modeling is carried out using numerical methods. Now the level of development of software numerical methods of three-dimensional gas-dynamic modeling of processes in turbomachinery makes it possible to determine with high accuracy the main characteristics of units at the design stage. It significantly reduces the time and cost of production. This article proposes a methodology for installation and improving the mathematical and grid model of HPT rotor blade to improve the quality of three-dimensional modeling. Aerodynamic processes mathematical modeling in aircraft turbojet engine blade rows is carried out using numerical methods. Grid model settings and turbulence model significantly affect the results qualitative characteristics and the calculations duration. This article proposes a methodology for grid model constructing based on local intense vortex formation and flow mixing places thickening. The influence of the grid and turbulence models parameters are estimated on the kinetic energy losses amount and secondary flows structure. The design model includes the building geometric model, preparation of the grid model and description of the turbulence model. Influence of grid and BSL and SST turbulence models on results of turbine blade aerodynamic calculation is considered in this article. Basic recommendations for the construction of mathematical and grid models in the ANSYS for uncooled rotor blades have been developed.

Performance enhancement of Savonius wind turbine by blade shape and twisted angle modifications

2021 ◽  
pp. 095765092098794
Author(s):  
Ahmed M Nagib Elmekawy ◽  
Hassan A Hassan Saeed ◽  
Sadek Z Kassab
Keyword(s):  
Wind Turbine ◽  
Performance Enhancement ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Vertical Axis ◽  
Cfd Simulations ◽  
Sliding Mesh ◽  
Blade Shape ◽  
Rotor Shape ◽  
Twisting Angle

Three-dimensional CFD simulations are carried out to study the increase of power generated from Savonius vertical axis wind turbines by modifying the blade shape and blade angel of twist. Twisting angle of the classical blade are varied and several proposed novel blade shapes are introduced to enhance the performance of the wind turbine. CFD simulations have been performed using sliding mesh technique of ANSYS software. Four turbulence models; realizable k -[Formula: see text], standard k - [Formula: see text], SST transition and SST k -[Formula: see text] are utilized in the simulations. The blade twisting angle has been modified for the proposed dimensions and wind speed. The introduced novel blade increased the power generated compared to the classical shapes. The two proposed novel blades achieved better power coefficients. One of the proposed models achieved an increase of 31% and the other one achieved 32.2% when compared to the classical rotor shape. The optimum twist angel for the two proposed models achieved 5.66% and 5.69% when compared with zero angle of twist.

Optimization of the Navy’s three-dimensional mine impact burial prediction simulation model, Impact35, using high-order numerical methods

2021 ◽  
pp. 154851292110286
Author(s):  
Athanasios Donas ◽  
Ioannis Famelis ◽  
Peter C Chu ◽  
George Galanis
Keyword(s):  
Numerical Analysis ◽  
Numerical Methods ◽  
Prediction Model ◽  
Simulation Model ◽  
Three Dimensional ◽  
Simulation System ◽  
High Order ◽  
Alternative Methodology ◽  
Runge Kutta ◽  
Fifth Order

The aim of this paper is to present an application of high-order numerical analysis methods to a simulation system that models the movement of a cylindrical-shaped object (mine, projectile, etc.) in a marine environment and in general in fluids with important applications in Naval operations. More specifically, an alternative methodology is proposed for the dynamics of the Navy’s three-dimensional mine impact burial prediction model, Impact35/vortex, based on the Dormand–Prince Runge–Kutta fifth-order and the singly diagonally implicit Runge–Kutta fifth-order methods. The main aim is to improve the time efficiency of the system, while keeping the deviation levels of the final results, derived from the standard and the proposed methodology, low.

scholarly journals Comparison of Two-Equation Turbulence Models for Prediction of Heat Transfer on Film-Cooled Turbine Blades

1997 ◽  
Author(s):  
Vijay K. Garg ◽  
Ali A. Ameri
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Computer Time ◽  
Suction Surface ◽  
The Heat Transfer Coefficient

A three-dimensional Navier-Stokes code has been used to compute the heat transfer coefficient on two film-cooled turbine blades, namely the VKI rotor with six rows of cooling holes including three rows on the shower head, and the C3X vane with nine rows of holes including five rows on the shower head. Predictions of heat transfer coefficient at the blade surface using three two-equation turbulence models, specifically, Coakley’s q-ω model, Chien’s k-ε model and Wilcox’s k-ω model with Menter’s modifications, have been compared with the experimental data of Camci and Arts (1990) for the VKI rotor, and of Hylton et al. (1988) for the C3X vane along with predictions using the Baldwin-Lomax (B-L) model taken from Garg and Gaugler (1995). It is found that for the cases considered here the two-equation models predict the blade heat transfer somewhat better than the B-L model except immediately downstream of the film-cooling holes on the suction surface of the VKI rotor, and over most of the suction surface of the C3X vane. However, all two-equation models require 40% more computer core than the B-L model for solution, and while the q-ω and k-ε models need 40% more computer time than the B-L model, the k-ω model requires at least 65% more time due to slower rate of convergence. It is found that the heat transfer coefficient exhibits a strong spanwise as well as streamwise variation for both blades and all turbulence models.

scholarly journals Numerical and experimental study on turbulence statistics in a large fan-stirred combustion vessel

2021 ◽  
Vol 62 (5) ◽  
Author(s):  
M. E. Morsy ◽  
J. Yang
Keyword(s):  
Isotropic Turbulence ◽  
Burning Velocity ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Turbulence Models ◽  
Initial Pressure ◽  
Dynamics Modeling ◽  
Turbulence Statistics ◽  
Experimental Conditions ◽  
Measured Velocity

Abstract Particle image velocimetry (PIV) has become a popular non-intrusive tool for measuring various types of flows. However, when measuring three-dimensional flows with two-dimensional (2D) PIV, there are some uncertainties in the measured velocity field due to out-of-plane motion, which might alter turbulence statistics and distort the overall flow characteristics. In the present study, three different turbulence models are employed and compared. Mean and fluctuating fields obtained by three-dimensional computational fluid dynamics modeling are compared to experimental data. Turbulence statistics such as integral length scale, Taylor microscale, Kolmogorov scale, turbulence kinetic energy, dissipation rate, and velocity correlations are calculated at different experimental conditions (i.e., pressure, temperature, fan speed, etc.). A reasonably isotropic and homogeneous turbulence with large turbulence intensities is achieved in the central region extending to almost 45 mm radius. This radius decreases with increasing the initial pressure. The influence of the third dimension velocity component on the measured characteristics is negligible. This is a result of the axisymmetric features of the flow pattern in the current vessel. The results prove that the present vessel can be conveniently adopted for several turbulent combustion studies including mainly the determination of turbulent burning velocity for gaseous premixed flames in nearly homogeneous isotropic turbulence. Graphic abstract

Study on Crankshaft Design Based on CAD/CAE

2011 ◽  
Vol 201-203 ◽  
pp. 830-835
Author(s):  
Chang Gao Xia ◽  
Jian Kuan Su ◽  
Mao Hui Pan
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Three Dimensional ◽  
Parametric Modeling ◽  
Analysis Procedure ◽  
Secondary Development ◽  
Design Quality ◽  
Element Analysis ◽  
Integrated Method ◽  
Engine Crankshaft

This paper presents an integrated method, which is based on the CAD/CAE, for engine crankshaft design. A parametric modeling system of engine crankshaft is established with the CATIA secondary development tools. Taking advantage of the finite element analysis procedure of engine crankshaft strength which is programmed with ANSYS APDL programming language, the parametric loading, automatic solution and result analysis of the crankshaft strength can be realized. Integrating the parametric modeling system of engine crankshaft and the special finite element analysis procedure of the engine crankshaft strength, the three-dimensional digital model of the crankshaft can be generated rapidly. By changing the structure dimension, the crankshaft series design is achieved and the design and analysis can be improved. Therefore, it is helpful to improve the design quality and efficiency of crankshaft and shorten the design cycle.

Multi-Objective Optimization of a Microturbine Compact Recuperator

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
Diego Micheli ◽  
Valentino Pediroda ◽  
Stefano Pieri
Keyword(s):  
Heat Transfer ◽  
Three Dimensional ◽  
Numerical Procedure ◽  
Design Procedure ◽  
Domain Size ◽  
Multidisciplinary Optimization ◽  
Computational Domain ◽  
Surface Geometry ◽  
Multi Objective ◽  
Flux Boundary Conditions

An automatic approach for the multi-objective shape optimization of microgas turbine heat exchangers is presented. According to the concept of multidisciplinary optimization, the methodology integrates a CAD parametric model of the heat transfer surfaces, a three-dimensional meshing tool, and a CFD solver, all managed by a design optimization platform. The repetitive pattern of the surface geometry has been exploited to reduce the computational domain size, and the constant flux boundary conditions have been imposed to better suit the real operative conditions. A new approach that couples cold and warm fluids in a periodic unitary cell is introduced. The effectiveness of the numerical procedure was verified comparing the numerical results with available literature data. The optimization objectives are maximizing the heat transfer rate and minimizing both friction factor and heat transfer surface. The paper presents the results of the optimization of a 50kWMGT recuperator. The design procedure can be effectively extended and applied to any industrial heat exchanger application.

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