scholarly journals Development of a robust solver to model the flow inside the engines for high-speed propulsion

2019 ◽  
Vol 304 ◽  
pp. 03013
Author(s):  
Ludovico Nista ◽  
Bayindir H. Saracoglu
Keyword(s):  
High Speed ◽  
Time Discretization ◽  
Propulsion System ◽  
Navier Stokes ◽  
Complex Flow ◽  
Riemann Solvers ◽  
Flow Physics ◽  
Multiple Test ◽  
Stability Robustness ◽  
Volume Method

The demand for discovering new commercial routes as well as the possibility to shortening civilian long-haul flights boosted the interest of civil hypersonic vehicle designs. Among all the multiple projects started by the various nations, the European community funded project STRATOFLY aims at refining the baseline LAPCAT II-MR2.4 design for further improvements. The new aircraft would enable a flight shorter that 3 hours from Brussels to Sydney, carrying 300-passengers above the already crowed atmosphere. The wide Mach range operability, up to Mach 8, demands the use of multiple engines, leading to a highly integrated propulsion system. The current study is focused on the development of new CFD platform to estimate the performance of the combined propulsion system during the supersonic to hypersonic transition. In order to control the complex flow physics, highfidelity CFD simulations remain the fundamental tools for the preliminary investigations. On the current framework, an advanced robust compressible solver has been develop d in order to handle the different flow regimes. The new tool solves Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations by employing cell-centered Finite Volume Method constructed on openFoam toolbox. Two innovative high-order discretization schemes, with different abilities, based on approximated Riemann solvers were developed for capturing the flow physics within high-speed propulsion systems. Advanced time discretization has been taken into account to increase the temporal accuracy. At the end, the whole implementation has been validated in multiple test cases, ranging from incompressible to hypersonic regimes, confirming its excellent stability, robustness and accuracy.

NUMERICAL PREDICTION OF VERTICAL SHIP MOTIONS AND ADDED RESISTANCE

2021 ◽  
Vol 159 (A4) ◽  
Author(s):  
F Cakici ◽  
E Kahramanoglu ◽  
A D Alkan
Keyword(s):  
Deep Water ◽  
High Speed ◽  
Computer Experiments ◽  
Navier Stokes ◽  
Ship Motions ◽  
Added Resistance ◽  
Strip Theory ◽  
Head Waves ◽  
Computational Fluid Dynamics Cfd ◽  
Volume Method

Along with the development of computer technology, the capability of Computational Fluid Dynamics (CFD) to conduct ‘virtual computer experiments’ has increased. CFD tools have become the most important tools for researchers to deal with several complex problems. In this study, the viscous approach called URANS (Unsteady Reynolds Averaged Navier-Stokes) which has a fully non-linear base has been used to solve the vertical ship motions and added resistance problems in head waves. In the solution strategy, the FVM (Finite Volume Method) is used that enables numerical discretization. The ship model DTMB 5512 has been chosen for a series of computational studies at Fn=0.41 representing a high speed case. Firstly, by using CFD tools the TF (Transfer Function) graphs for the coupled heave- pitch motions in deep water have been generated and then comparisons have been made with IIHR (Iowa Institute of Hydraulic Research) experimental results and ordinary strip theory outputs. In the latter step, TF graphs of added resistance for deep water have been generated by using CFD and comparisons have been made only with strip theory.

Numerical Prediction of Vertical Ship Motions and Added Resistance

2017 ◽  
Vol 159 (A4) ◽  
Author(s):  
F Cakici ◽  
E Kahramanoglu ◽  
A D Alkan
Keyword(s):  
Deep Water ◽  
High Speed ◽  
Computer Experiments ◽  
Navier Stokes ◽  
Ship Motions ◽  
Added Resistance ◽  
Strip Theory ◽  
Head Waves ◽  
Computational Fluid Dynamics Cfd ◽  
Volume Method

Along with the development of computer technology, the capability of Computational Fluid Dynamics (CFD) to conduct ‘virtual computer experiments’ has increased. CFD tools have become the most important tools for researchers to deal with several complex problems. In this study, the viscous approach called URANS (Unsteady Reynolds Averaged Navier-Stokes) which has a fully non-linear base has been used to solve the vertical ship motions and added resistance problems in head waves. In the solution strategy, the FVM (Finite Volume Method) is used that enables numerical discretization. The ship model DTMB 5512 has been chosen for a series of computational studies at Fn=0.41 representing a high speed case. Firstly, by using CFD tools the TF (Transfer Function) graphs for the coupled heave-pitch motions in deep water have been generated and then comparisons have been made with IIHR (Iowa Institute of Hydraulic Research) experimental results and ordinary strip theory outputs. In the latter step, TF graphs of added resistance for deep water have been generated by using CFD and comparisons have been made only with strip theory.

Hybrid RANS-LES Modeling of the Aerothermal Field in an Annular Hot Streak Generator for the Study of Combustor–Turbine Interaction

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
A. Andreini ◽  
T. Bacci ◽  
M. Insinna ◽  
L. Mazzei ◽  
S. Salvadori
Keyword(s):  
Navier Stokes ◽  
Test Rig ◽  
Complex Flow ◽  
Lean Burn ◽  
Flow Physics ◽  
Safety Margins ◽  
Viable Approach ◽  
Sas Model ◽  
Aero Engines ◽  
Eu Project

The adoption of lean-burn technology in modern aero-engines influences the already critical aerothermal conditions at turbine entry, where the absence of dilution holes preserves the swirl component generated by burners and prevents any control on pattern factor. The associated uncertainty and lack of confidence entail the application of wide safety margins in turbine cooling design, with a detrimental effect on engine efficiency. Computational fluid dynamics (CFD) can provide a deeper understanding of the physical phenomena involved in combustor–turbine interaction, especially with hybrid Reynolds-averaged Navier–Stokes (RANS) large eddy simulation (LES) models, such as scale adaptive simulation (SAS), which are proving to overcome the well-known limitations of the RANS approach and be a viable approach to capture the complex flow physics. This paper describes the numerical investigation on a test rig representative of a lean-burn, effusion cooled, annular combustor developed in the EU Project Full Aerothermal Combustor-Turbine interactiOns Research (FACTOR) with the aim of studying combustor–turbine interaction. Results obtained with RANS and SAS were critically compared to experimental data and analyzed to better understand the flow physics, as well as to assess the improvements related to the use of hybrid RANS-LES models. Significant discrepancies are highlighted for RANS in predicting the recirculating region, which has slight influence on the velocity field at the combustor outlet, but affects dramatically mixing and the resulting temperature distribution. The accuracy of the results achieved suggests the exploitation of SAS model with a view to the future inclusion of the nozzle guide vanes in the test rig.

Propulsive jets and their acoustics

2007 ◽  
Vol 365 (1859) ◽  
pp. 2443-2467 ◽  
Author(s):  
Alexander N Secundov ◽  
Stanley F Birch ◽  
Paul G Tucker
Keyword(s):  
Navier Stokes ◽  
Jet Flows ◽  
Complex Flow ◽  
Flow Physics ◽  
Eddy Simulation ◽  
Daunting Task ◽  
Wide Range ◽  
Large Eddy ◽  
Computational Resources ◽  
Hybrid Forms

The complex flow physics challenges and asks questions regarding these challenges a wide range of jet flows found in aerospace engineering. Hence, the daunting task facing Reynolds-averaged Navier–Stokes (RANS) technology, for which the time average of the turbulent flow field is solved, is set out. Despite the clear potential of large eddy simulation (LES)-related methods and hybrid forms involving some RANS modelling, numerous current deficiencies, mostly related to the limitations of computational resources, are identified. It is concluded that currently, these limitations make LES and hybrids most useful for understanding flow physics and refining RANS technology. The use of LES in conjunction with a ray-tracing model to elucidate the physics of acoustic wave transmission in jets and thus improved RANS technology is described. It is argued that, as a stopgap measure, pure RANS simulations can be a valuable part of the design process and can now predict acoustics spectra and directivity diagrams with useful accuracy. Ultimately, hybrid RANS–LES-type methods, and then pure LES, will dominate, but the time-scales for this transition suggests that improvements to RANS technology should not be ignored.

Thermoacoustic and buoyancy-driven transport in a square side-heated cavity filled with a near-critical fluid

1996 ◽  
Vol 316 ◽  
pp. 53-72 ◽  
Author(s):  
Bernard Zappoli ◽  
Sakir Amiroudine ◽  
Pierre Carles ◽  
Jalil Ouazzani
Keyword(s):  
High Speed ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Square Cavity ◽  
Piston Effect ◽  
Navier Stokes Equations ◽  
Significant Difference ◽  
Buoyancy Driven Convection ◽  
Volume Method ◽  
Very High

The mechanisms of heat and mass transport in a side-heated square cavity filled with a near-critical fluid are explored, with special emphasis on the interplay between buoyancy-driven convection and the Piston Effect. The Navier–Stokes equations for a near-critical van der Waals gas are solved numerically by means of an acoustically filtered, finite-volume method. The results have revealed some striking behaviour compared with that obtained for normally compressible gases: (i) heat equilibration is still achieved rapidly, as under zero-g conditions, by the Piston Effect before convection has time to enhance heat transport; (ii) mass equilibration is achieved on a much longer time scale by quasi-isothermal buoyant convection; (iii) due to the very high compressibility, a stagnation-point effect similar to that encountered in high-speed flows provokes an overheating of the upper wall; and (iv) a significant difference to the convective single-roll pattern generated under the same conditions in normal CO2 is found, in the form of a double-roll convective structure.

Interceptor hydrodynamic analysis for handling trim control problems in the high-speed crafts

2011 ◽  
Vol 225 (11) ◽  
pp. 2597-2618 ◽  
Author(s):  
H Ghassemi ◽  
M Mansouri ◽  
S Zaferanlouei
Keyword(s):  
High Speed ◽  
Stokes Equations ◽  
Contact Point ◽  
Simple Algorithm ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Hydrodynamic Analysis ◽  
Drag Forces ◽  
Variable Mode ◽  
Volume Method

In this study, the effects of hydrodynamic interceptors on fast crafts are investigated to find their optimum geometrical characteristics based on numerical methods. Interceptors are vertical blades installed symmetrically at the aft of the craft. They are designed either fixed or variable. In variable mode, interceptors’ heights are adjusted by various mechanisms. They also cause changes in pressure disruption around the craft and especially at the end of the hull. The pressure variations have an effect on draft height and lifting forces which directly results in a better control of trim. Using the computational fluid dynamics, the pressure distribution around the hull and its effects on trim are computed and then discussed. The Reynolds Average Navier–Stokes equations are also applied to model the flow around the fixed flat and wedge craft with an interceptor at different heights. The model is analysed based on finite volume method and SIMPLE algorithm using dynamic mesh. The results show that the interceptor causes an intense pressure rate in its contact point. It also decreases the wet surface of the craft and drag forces coefficient. At last, they lead to a better control of trim. The height of interceptor has an important effect on its efficiency and it should be selected according to the speed of the craft.

Blade Tip Carving Effects on the Aerothermal Performance of a Transonic Turbine

2014 ◽  
Vol 137 (2) ◽  
Author(s):  
C. De Maesschalck ◽  
S. Lavagnoli ◽  
G. Paniagua
Keyword(s):  
High Speed ◽  
Thermal Stresses ◽  
Numerical Study ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Geometrical Parameters ◽  
Complex Flow ◽  
Leakage Flows ◽  
Blade Tip ◽  
Exit Mach Number

Tip leakage flows in unshrouded high speed turbines cause large aerodynamic penalties, induce significant thermal loads and give rise to intense thermal stresses onto the blade tip and casing endwalls. In the pursuit of superior engine reliability and efficiency, the turbine blade tip design is of paramount importance and still poses an exceptional challenge to turbine designers. The ever-increasing rotational speeds and pressure loadings tend to accelerate the tip flow velocities beyond the transonic regime. Overtip supersonic flows are characterized by complex flow patterns, which determine the heat transfer signature. Hence, the physics of the overtip flow structures and the influence of the geometrical parameters require further understanding to develop innovative tip designs. Conventional blade tip shapes are not adequate for such high speed flows and hence, potential for enhanced performances lays in appropriate tip shaping. The present research aims to quantify the prospective gain offered by a fully contoured blade tip shape against conventional geometries such as a flat and squealer tip. A detailed numerical study was conducted on a modern rotor blade (Reynolds number of 5.5 × 105 and a relative exit Mach number of 0.9) by means of three-dimensional (3D) Reynolds-averaged Navier–Stokes (RANS) calculations. Two novel contoured tip geometries were designed based on a two-dimensional (2D) tip shape optimization in which only the upper 2% of the blade span was modified. This study yields a deeper insight into the application of blade tip carving in high speed turbines and provides guidelines for future tip designs with enhanced aerothermal performances.

Numerical Study on Aerodynamic Performances of CRH3 under Crosswind

2012 ◽  
Vol 215-216 ◽  
pp. 992-997
Author(s):  
Hong Yuan Su ◽  
Ming Li ◽  
Dong Ping Wang ◽  
Feng Liu
Keyword(s):  
High Speed ◽  
Numerical Study ◽  
Lateral Force ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Aerodynamic Properties ◽  
Aerodynamic Performances ◽  
Volume Method ◽  
Incompressible Navier Stokes Equation ◽  
Multiple Units

Based on 3D steady and incompressible Navier-Stokes equation and standard k-ε turbulent model, numerical calculation for the aerodynamic properties of EMU (Electric Multiple Units) CRH3 (China Railway High-Speed 3)running in crosswind were carried out by finite volume method. Aerodynamic performances of EMU CRH3 were analyzed and compared, when the EMU was running in different speed and under the crosswinds of different velocity. The research showed that with the change of speed of train and crosswind, the surface pressure and aerodynamic forces altered according to a certain rule. Compared with the drag, the change of lift and lateral force caused by the increase of crosswind were more serious. When the speed of train was constant of 200km/h, 250km/h and 300km/h, the drag of train increased by 26.7%, 20.4% and 19.8% respectively as the speed of crosswind increased from 12.5m/s to 30m/s, the lift of train increased by 340.7%, 331.7% and 337.1% respectively, and the lateral force of train increases by 296.3%, 266.0% and 150.2% respectively. As the speed of crosswind increases, the increase of drag caused by the acceleration of train is more serious than lift and lateral force.

Simplified CFD based Approach for Estimation of Heat Flux over Wedge Models in High Speed Plasma Flows

2017 ◽  
Vol 67 (5) ◽  
pp. 497
Author(s):  
L. Aravindakshan Pillai ◽  
Praveen Nair
Keyword(s):  
Heat Flux ◽  
Numerical Simulations ◽  
High Speed ◽  
Complex Flow ◽  
Plasma Flows ◽  
Flow Physics ◽  
Blunt Bodies ◽  
Real Gas Effects ◽  
Computational Fluid Dynamics Cfd ◽  
Simplified Procedure

<p>Analysis of plasma flows at hypersonic velocity over blunt bodies is quite complex and challenging as it involves complex flow physics and carries several uncertainties. Simultaneous simulation of all the parameters as existing in re-entry flight puts constraints on most of the ground based experiments. Numerical simulations, on the other hand, require modelling of ionisation and real gas effects and prove to be computationally costly. This paper highlights the development of unstructured, cell centred second order accurate parallel version of in-house computational fluid dynamics (CFD) solver where high temperature equivalent properties used from Hansen’s 7 species model and establishment of a simplified procedure for estimation of heat flux over wedge models tested in Plasma Wind Tunnel facility, Vikram Sarabhai Space Centre. Numerical simulations were carried out for Plasma tunnel initially to get the flow properties inside the tunnel when operated without any model. A simplified CFD based approach is established for computing the heat flux over the bodies tested inside the tunnel and compared with the measured data. The comparison of numerical and measured values shows that the proposed methodology captures the flow physics and various parameters with acceptable levels of accuracy.</p>

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