scholarly journals A Consistent and Implicit Rhie–Chow Interpolation for Drag Forces in Coupled Multiphase Solvers

2021 ◽  
Vol 6 (2) ◽  
pp. 7
Author(s):  
Lucian Hanimann ◽  
Luca Mangani ◽  
Marwan Darwish ◽  
Ernesto Casartelli ◽  
Damian M. Vogt
Keyword(s):  
Flow Simulation ◽  
Fluid Flows ◽  
Substantial Improvement ◽  
Test Case ◽  
Drag Forces ◽  
Flow Coupling ◽  
Dilute Gas ◽  
Finite Volume Discretization ◽  
Commercial Code ◽  
And Performance

The use of coupled algorithms for single fluid flow simulation has proven its superiority as opposed to segregated algorithms, especially in terms of robustness and performance. In this paper, the coupled approach is extended for the simulation of multi-fluid flows, using a collocated and pressure-based finite volume discretization technique with a Eulerian–Eulerian model. In this context a key ingredient in this method is extending the Rhie–Chow interpolation technique to account for the unique flow coupling that arises from inter-phase drag. The treatment of this inter-fluid coupling and the fashion in which it interacts with the velocity-pressure solution algorithm is presented in detail and its effect on robustness and accuracy is demonstrated using 2D dilute gas–solid flow test case. The results achieved with this technique show substantial improvement in accuracy and performance when compared to a leading commercial code for a transonic nozzle configuration.

Sailboat Hydrodynamic Drag Source Prediction and Performance Assessment

1991 ◽  
Author(s):  
Charles W. Boppe
Keyword(s):  
Flow Simulation ◽  
Surface Friction ◽  
Approximate Model ◽  
Hydrodynamic Performance ◽  
Hydrodynamic Drag ◽  
Important Place ◽  
Drag Forces ◽  
Induced Drag ◽  
Velocity Prediction ◽  
And Performance

Velocity Prediction Programs used for sailboat hull, sail, and keel sizing trades, have found an important place in the designer's toolbox. Sail designers now recognize the benefits of applying aerodynamic panel methods. In addition, the 1983 and 1987 America's Cup competitions have drawn attention to use of computerized flow simulation methods for improving hydrodynamic performance. This paper highlights characteristics of methods capable of predicting sailboat hydrodynamic drag forces. Taken together the resistance components predicted include appendage surface friction drag, configuration and lift-induced drag, and configuration trim drag. All of the computer programs discussed in this paper were originally developed for aircraft aerodynamic applications. Since each method is based on some approximate model of real world flow physics, the need to establish a simulation experience base is emphasized and illustrated. VPP polar diagrams are used to link drag source benefits and penalties to sailboat performance. Micro-computer execution times are provided because the methods described operate in machines commonly found in the naval architect’s office.

scholarly journals Distributing Load Flow Computations Across System Operators Boundaries Using the Newton–Krylov–Schwarz Algorithm Implemented in PETSc

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2910
Author(s):  
Stefano Rinaldo  ◽  
Andrea Ceresoli  ◽  
Domenico Lahaye  ◽  
Marco Merlo  ◽  
Miloš  Cvetković ◽  
...  
Keyword(s):  
Power Flow ◽  
Flow Analysis ◽  
Flow Simulation ◽  
Load Flow ◽  
Inexact Newton Method ◽  
Test Case ◽  
Flow Solver ◽  
Cross Border ◽  
System Operator ◽  
Schwarz Algorithm

The upward trends in renewable energy penetration, cross-border flow volatility and electricity actors’ proliferation pose new challenges in the power system management. Electricity and market operators need to increase collaboration, also in terms of more frequent and detailed system analyses, so as to ensure adequate levels of quality and security of supply. This work proposes a novel distributed load flow solver enabling for better cross border flow analysis and fulfilling possible data ownership and confidentiality arrangements in place among the actors. The model exploits an Inexact Newton Method, the Newton–Krylov–Schwarz method, available in the portable, extensible toolkit for scientific computation (PETSc) libraries. A case-study illustrates a real application of the model for the TSO–TSO (transmission system operator) cross-border operation, analyzing the specific policy context and proposing a test case for a coordinated power flow simulation. The results show the feasibility of performing the distributed calculation remotely, keeping the overall simulation times only a few times slower than locally.

scholarly journals Integration Model between Heterogeneous Data Services in a Cloud

2021 ◽  
Vol 27 (4) ◽  
pp. 387-412
Author(s):  
Marcelo Aires Vieira ◽  
Elivaldo Lozer Fracalossi Ribeiro ◽  
Daniela Barreiro Claro ◽  
Babacar Mane
Keyword(s):  
Heterogeneous Data ◽  
Cloud Services ◽  
Test Case ◽  
Integration Model ◽  
Data Services ◽  
On Demand ◽  
Database As A Service ◽  
And Performance ◽  
Data As A Service ◽  
Integrate Data

With the growth of cloud services, many companies have begun to persist and make their data available through services such as Data as a Service (DaaS) and Database as a Service (DBaaS). The DaaS model provides on-demand data through an Application Programming Inter- face (API), while DBaaS model provides on-demand database management systems. Different data sources require efforts to integrate data from different models. These model types include unstructured, semi-structured, and structured data. Heterogeneity from DaaS and DBaaS makes it challenging to integrate data from different services. In response to this problem, we developed the Data Join (DJ) method to integrate heterogeneous DaaS and DBaaS sources. DJ was described through canonical models and incorporated into a middleware as a proof-of-concept. A test case and three experiments were performed to validate our DJ method: the first experiment tackles data from DaaS and DBaaS in isolation; the second experiment associates data from different DaaS and DBaaS through one join clause; and the third experiment integrates data from three sources (one DaaS and two DBaaS) based on different data type (relational, NoSQL, and NewSQL) through two join clauses. Our experiments evaluated the viability, functionality, integration, and performance of the DJ method. Results demonstrate that DJ method outperforms most of the related work on selecting and integrating data in a cloud environment.

scholarly journals Flow Simulation And Performance Analysis Of Centrifugal Compressor Using Cfd_Tool

2021 ◽  
Vol 23 (11) ◽  
pp. 693-703
Author(s):  
Tesfaye Barza ◽  
◽  
G. Lakshmikanth ◽  
Keyword(s):  
Performance Analysis ◽  
Pressure Distribution ◽  
Turbulence Model ◽  
Centrifugal Compressor ◽  
Flow Simulation ◽  
Internal Flow ◽  
Design System ◽  
Turbulent Fluid Flow ◽  
Compressor Impeller ◽  
And Performance

This paper is concerned the flow simulation and performance analysis of the Centrifugal Compressor Using CFD – Tool. The complex internal flow of centrifugal compressor can be well analyzed, and the unique design system needs to be developed. It should be early to use the interface and also flexible for input and output. A 3-D flow simulation of turbulent – fluid flow is presented to visualize the flow pattern in-terms of velocity, streamline and pressure distribution on the blade surface are graphically interpreted. The standard K- e turbulence model and the simple model algorithm were chosen for turbulence model and pressure distribution well determined. The simulation was steady Heat transfer and moving reference frame was used to consider the impeller interaction under high resolution. Furthermore, A computational Fluid Dynamics (CFD) 3-D simulation is done to analyze the impeller head and efficiency required of centrifugal compressor. The impeller is rotated for a constant revolution and mass flow rate, in this study initially the geometry of centrifugal compressor impeller is created by an ANSYS Vista CCD, and the Blade modeller done by Bladegen, Finally, CFD analysis was performed in ANSYS CFX using the ANSYS Turbo grid meshing tool. According to the analysis, as the number of impeller blades increases, so does the value of the head and power imparted, as well as the impeller’s efficiency.

Upwind Sail Performance Prediction for a VPP including “Flying Shape” Analysis

2009 ◽  
Author(s):  
Brian Maskew ◽  
Frank DeBord
Keyword(s):  
Grid Point ◽  
Flow Simulation ◽  
Lattice Method ◽  
Prediction Program ◽  
Aerodynamic Pressure ◽  
Dynamic Velocity ◽  
Velocity Prediction ◽  
Coupled Structures ◽  
And Performance ◽  
Ultimate Objective

A coupled aerodynamic/structures approach is presented for predicting the flying shape and performance of yacht sails in upwind conditions. The method is incorporated in a flow simulation computer program, and is part of an ultimate objective for a simultaneous aeroelastic/hydro analysis in a Dynamic Velocity Prediction Program (DVPP), that will include a 6DOF motion solver, and at some point could include calculations in waves. The time-stepping aerodynamic module uses an advanced vortex lattice method for the sails and a panel method with special base separation treatment to represent the abovewater part of the hull and mast. A coupled inverse boundary layer analysis is applied on all surfaces including both sides of each sail membrane; this computes the skinfriction drag and the source displacement effects of the boundary layers and wakes, including bubble and leeside “trailing-edge” type separations. . At each step, the computed aerodynamic pressure and skin-friction loads are transferred to a coupled structures module that uses a network grid of tension “cords” in each sail membrane, each cord representing a collection of fiber “strings”. The solution of a structural equilibrium matrix provides the displacements needed to achieve balance between the aerodynamic and tension loads at each grid point as the shape iterations proceed. Details of the methodology used are presented and comparisons of predicted aerodynamic forces to wind tunnel results and an existing VPP sail model are provided. In addition, predictions are compared to some simple experiments to demonstrate the aerodynamic/structural coupling necessary to predict flying shape. Finally, an outline is given for incorporation of this methodology into the planned Dynamic Velocity Prediction Program.

A Study of Impeller-Diffuser-Volute Interaction in a Centrifugal Fan

2005 ◽  
Vol 127 (1) ◽  
pp. 84-90 ◽  
Author(s):  
Tarek Meakhail ◽  
Seung O. Park
Keyword(s):  
Simulation Model ◽  
Velocity Measurement ◽  
Measurement Data ◽  
Flow Simulation ◽  
Separated Flow ◽  
Quantitative Agreement ◽  
Initial Guess ◽  
Centrifugal Fan ◽  
Vaned Diffuser ◽  
Commercial Code

This paper reports velocity measurement data in the interaction region between the impeller and vaned diffuser and the results of numerical flow simulation of the whole machine (impeller, vaned diffuser and volute) of a single stage centrifugal fan. Two-dimensional instantaneous velocity measurement is done using particle image velocimetry (PIV). Numerical simulation of impeller-diffuser-volute interaction is performed using CFX-Tascflow commercial code. A frozen rotor simulation model is used for the steady calculation and a rotor-stator simulation model is used for the unsteady calculation using the steady results as an initial guess. The simulation results show that the separated flow regime near the diffuser hub extends to the volute. Comparison between the unsteady computation and those of measurement indicates that the rotor/stator model employed in the simulation predicts essential characteristics of unsteady flow in the centrifugal fan. However, quantitative agreement remains rather poor.

Effects of Circumferential Inlet Distortion on the Performance of a Transonic Fan Together With the Impact of Tip Injection

2016 ◽  
Author(s):  
Hossein Khaleghi ◽  
Reza Jalaly
Keyword(s):  
Flow Field ◽  
Axial Flow ◽  
Test Case ◽  
Inlet Distortion ◽  
Distorted Region ◽  
And Performance ◽  
Tip Injection ◽  
The Stability ◽  
Transonic Fan ◽  
The Impact

Half-annulus unsteady numerical simulations have been conducted with a 60-deg total pressure circumferential distortion in a transonic axial-flow fan. The effects of inlet distortion on the performance, stability and flow field of the test case are investigated and analyzed. Results show that the incidence angles are reduced when the blades are entering into the distorted region. Conversely, distortion increases the incidence angles onto the blades when they are leaving the distorted section. Results further reveal that the time-averaged flow field at the tip of the blade is similar with and without distortion. However, the distortion applied is found to have detrimental effects on both the stability and performance. The impacts of both annular and discrete tip injection on the endwall flow field are further studied in the current work. It is shown that endwall injection reduces the incidence angles onto the blades. Consequently, the passage shock and the leakage flow are pushed rearward, which postpones stall initiation.

Automatic Optimisation of Pre-Swirl Nozzle Design

2006 ◽  
Author(s):  
Fabio Ciampoli ◽  
John W. Chew ◽  
Shahrokh Shahpar ◽  
Elisabeth Willocq
Keyword(s):  
Geometric Model ◽  
Stress Constraints ◽  
Hill Climbing ◽  
Surface Model ◽  
Test Case ◽  
Performance Improvements ◽  
Whole Process ◽  
And Performance ◽  
Rsm Model ◽  
Optimisation Methods

The objective of the research described here is to develop and demonstrate use of automatic design methods for pre-swirl nozzles. Performance of pre-swirled cooling air delivery systems depends critically on the design of these nozzles which is subject to manufacturing and stress constraints. The best solution may be a compromise between cost and performance. Here it is shown that automatic optimisation using computational fluid dynamics (CFD) to evaluate nozzle performance can be useful in design. A parametric geometric model of a nozzle with appropriate constraints is first defined and the CFD meshing and solution are then automated. The mesh generation is found to be the most delicate task in the whole process. Direct hill climbing (DHC) and response surface model (RSM) optimisation methods have been evaluated. For the test case considered, significant nozzle performance improvements were obtained using both methods, but the RSM model was preferred.

Design and Analysis of a Marine Current Turbine

2017 ◽  
Author(s):  
T. Karthikeyan ◽  
E. J. Avital ◽  
N. Venkatesan ◽  
A. Samad
Keyword(s):  
Pitch Angle ◽  
Flow Simulation ◽  
Ocean Current ◽  
Power Coefficient ◽  
Design Parameters ◽  
Marine Current Turbine ◽  
Commercial Code ◽  
Marine Current ◽  
Current Turbine ◽  
Blade Pitch Angle

Ocean stores a huge amount of energy and ocean current energy can be a viable source in future. In this article, an axial marine current turbine has been optimized to enhance its power coefficient through numerical modeling. The blade pitch-angle and number of blades are the design parameters chosen for the analysis to find the optimal design. A commercial code for CFD simulations with in-house optimization code was used for the analysis. It was found that, changing the blade pitch-angle and reducing the number of blades can improve the turbine’s coefficient of power. This is due to increase in lift and reduction of losses caused by turbulence near the downstream of the turbine. The article presents flow-simulation difficulties and characteristic curves to identify the differences between the actual and optimized turbine. The detailed flow physics is discussed and pictured in the post processed plots.

CFD Studies on the Performance of a Centrifugal Compressor With Single Wall Rotating Vaneless Diffusers at the Wall Extension Ratios of 1.1 and 1.15

2017 ◽  
Author(s):  
Srinivasa Rao Konakala ◽  
Mukka Govardhan
Keyword(s):  
Centrifugal Compressor ◽  
Total Pressure ◽  
Static Pressure ◽  
Substantial Improvement ◽  
Significant Loss ◽  
Vaneless Diffuser ◽  
Shear Forces ◽  
Overall Performance ◽  
Vaneless Diffusers ◽  
And Performance

Efficiency of the centrifugal compressor is affected by non-uniform flow at the exit of the impeller and the losses in the diffuser. This causes a significant loss of total pressure and drop in the performance of a centrifugal compressor. By rotating some portion of stationary vaneless diffuser walls with the speed of the impeller, the shear forces between the flow and diffuser walls are greatly reduced. Thereby improvement in the operating range and performance is achieved. This paper presents CFD studies on the effect of different single wall rotations i.e. hub rotation and shroud rotation of the vaneless diffusers on the overall performance at 10% and 15% extension of impeller walls. It is observed that the performance characteristics of compressors with all RVD models offer higher static pressure recovery and also higher rate of diffusion compared to the base compressor with SVD. It is clear that as extended radius increases from 10% to 15%, substantial improvement of efficiency and reduction of losses are observed for both type of models. Out of two single wall rotation models, SRVD model is able to better mix the jet-wake type of impeller exit flows and minimizes the losses therein and improve the performance of the centrifugal compressor.

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