Design of Curved Annular Diffusers

2020 ◽  
Vol 142 (4) ◽  
Author(s):  
Vinayender Kuchana ◽  
N. Balakrishnan ◽  
Balamurugan Srinivasan
Keyword(s):  
Design Space ◽  
Pressure Gradients ◽  
Cfd Simulations ◽  
Maximum Slope ◽  
Pressure Fields ◽  
Annular Diffuser ◽  
Computational Fluid Dynamics Cfd ◽  
Curvature Distribution ◽  
Automated Optimization ◽  
End Wall

Abstract Influence of curvature distribution and area-ratio (AR) distribution on the pressure fields within the curved annular diffuser are discussed. General guidelines for end-wall contouring to control the pressure gradients on the diffuser walls are evolved and further demonstrated through computational fluid dynamics (CFD) simulations. Also, detailed guidelines for controlling the adverse pressure gradients (APG) on duct walls are presented. A geometry generation methodology (GGM) which enables both design and evaluation of curved annular diffusers based on the guidelines evolved is presented. The approach presented deals with the sensitivity of the duct performance parameters to duct wall modifications. In that sense, the work per se is not a description of an automated optimization process, but rather about the physical principles that can guide such an optimization. An aggressive diffuser design space is identified with ducts of maximum slope of 50 deg and maximum divergence angle between the outer and inner walls of 10 deg for length to inlet height ratio ranging from 1.25 to 2.5. Part of the identified design space for which the flow separation can be eliminated based on the guidelines evolved is demarcated. The need for flow control, possibly passive, is established for more aggressive designs.

Bulbous Bow Retrofit of a Containership Using an Open Source Computational Fluid Dynamics (CFD) Toolbox

2014 ◽  
Author(s):  
Grzegorz Filip ◽  
Dae-Hyun Kim ◽  
Sunil Sahu ◽  
Jan de Kat ◽  
Kevin Maki
Keyword(s):  
Open Source ◽  
Design Space ◽  
Exploration And Exploitation ◽  
Cfd Simulations ◽  
Slow Steaming ◽  
Parameterized Design ◽  
Computational Fluid Dynamics Cfd ◽  
Bulbous Bow ◽  
Alternative Designs ◽  
Propeller Performance

This paper describes a numerical bulbous bow retrofit analysis for a modern container ship operating under a slow-steaming profile. The retrofit analysis is used as an example of a design process based on high-fidelity CFD simulations and surrogate modelling. The bulbous bow design candidates are generated through a parametric modification of the original bow geometry. The alternative designs are evaluated using the open-source CFD toolbox OpenFOAM and the computed effective power predictions are used to rank each design across the entire operating profile. Additionally, the influence of the alternative bulb designs on the wave-making resistance and the propeller performance is examined in detail. Surrogate models are then used to explore the parameterized design space and to establish a sequence of design exploration and exploitation cycles in the retrofit analysis with the ultimate goal of generating an improved bow shape.

Comparison of Two-Dimensional and Three-Dimensional Turbine Airfoils in Combination With Nonaxisymmetric Endwall Contouring

2017 ◽  
Vol 139 (6) ◽  
Author(s):  
Tobias W. Zimmermann ◽  
Oliver Curkovic ◽  
Manfred Wirsum ◽  
Andrew Fowler ◽  
Kush Patel
Keyword(s):  
Three Dimensional ◽  
Cfd Simulations ◽  
Positive Effects ◽  
Beneficial Impact ◽  
Flow Phenomena ◽  
Computational Fluid Dynamics Cfd ◽  
Endwall Contouring ◽  
Turbine Airfoils ◽  
End Wall ◽  
Constant Section

Tangential endwall contouring (TEWC) is intended to improve the turbomachinery blading efficiency. This paper summarizes the experimental and numerical investigation of a test turbine with endwall contoured vanes and blades. Constant section (2D) airfoils as well as optimized compound lean (3D) high pressure steam turbine blading in baseline and endwall contoured configurations have been examined. Brush seals (BSs) are implemented within the casing sided cavities to minimize the leakage flow near the tip endwalls, where the contouring is also applied. The pressure and temperature data that are recorded in three axial measuring planes are plotted to visualize the change in flow structure. This shows that the efficiency is increased for 2D airfoils by means of endwall contouring. However, the efficiency of the first stage suffers, and the endwall contouring is still beneficial for the overall performance of the engine. Both phenomena (an efficiency loss in stage one and an improvement of the performance in stage two) have also been measured for the optimized 3D configurations; thus, it can be expected that the endwall contouring has also a beneficial impact on the performance of multirow turbines. The numerical investigations demonstrate in detail, how the secondary flow phenomena are influenced by end-wall contouring and a description of the changes in vortex formations as well as blade loading are given for the various configurations. It has been found that for steady computational fluid dynamics (CFD) simulations the use of stage interfaces suppresses the positive effects of the endwall contour onto the downstream blade row.

Parametric Model of Dead Leg Steady-State Thermal Performance

2018 ◽  
Author(s):  
Arnaud Sanchis ◽  
Sonny Andersson ◽  
Atle Jensen
Keyword(s):  
Low Temperatures ◽  
Design Space ◽  
Production Systems ◽  
Parametric Model ◽  
Thermal Design ◽  
Piping System ◽  
Cfd Simulations ◽  
System A ◽  
Novel Approach ◽  
Computational Fluid Dynamics Cfd

During thermal design of Subsea Production Systems (SPS), Computational Fluid Dynamics (CFD) is used to calculate production fluid temperatures in dead legs of the system. One purpose of such simulations could be to calculate the amount of insulation needed to avoid low temperatures in the piping system. A novel approach to this type of analysis is presented here to build a parametric model able to map the dead leg performance against any set of input parameters. The workflow relies on a response surface analysis performed from the results of a limited set of CFD simulations run on a sparse simulation matrix that covers the design space. Once generated, the parametric model provides real-time results and may be used for screening, optimization or condition monitoring purposes.

Optimized Laminar Axisymmetrical Nozzle Design Using a Numerically Validated Thwaites Method

2012 ◽  
Vol 134 (10) ◽  
Author(s):  
Philippe Versailles ◽  
Jeffrey M. Bergthorson
Keyword(s):  
Design Tool ◽  
Pressure Gradients ◽  
Efficient Design ◽  
Internal Flows ◽  
Cfd Simulations ◽  
Integral Boundary ◽  
Design And Optimization ◽  
Computational Fluid Dynamics Cfd ◽  
Historical Developments ◽  
Good Agreement

This paper presents the Thwaites method as an accurate and efficient design tool for laminar, axisymmetrical nozzles. Based on historical developments, it is improved to describe internal flows with highly favorable pressure gradients in cylindrical coordinates. The calculation of the core flow velocity distribution based on the continuity equation is proposed as a replacement to other sophisticated numerical methods. A remarkably good agreement is obtained when comparing the results of the current Thwaites method against those of computational fluid dynamics (CFD) simulations, for which the integral boundary layer thicknesses are calculated with equations developed from first principles in the course of the work. This consistency among the results and the low time and resource costs of the Thwaites method confirm its applicability and usefulness as an engineering design and optimization tool.

Optimized Design of Wastewater Disinfection Reactors Based on an Artificial Neural Network Metamodel

2016 ◽  
Author(s):  
Wangshu Wei ◽  
Charles N. Haas ◽  
Bakhtier Farouk
Keyword(s):  
Wastewater Treatment ◽  
Design Space ◽  
Sampling Technique ◽  
Optimized Design ◽  
Hydraulic Characteristics ◽  
Cfd Simulations ◽  
Performance Space ◽  
Wastewater Disinfection ◽  
Treatment Facilities ◽  
Computational Fluid Dynamics Cfd

Peracetic acid (PAA) is an emerging disinfectant for the treatment of wastewater. While it would be possible to optimize the design of this system using computational fluid dynamics (CFD), the computational intensity would be high. As an alternative, we show that an Artificial Neutral Network (ANN) based metamodel can approximate the CFD solutions over an 11 dimensional performance space (dimensions, hydraulic characteristics, and chemical kinetics). By sampling the design space using a quasi-random sampling technique, a series of CFD simulations of disinfection characteristics of PAA in a wastewater treatment reactor are carried out. After a training process using 40 different CFD runs are completed, the ANN developed can be used to achieve an optimized design of wastewater treatment facilities with minimal total cost and acceptable disinfection performance efficiency.

scholarly journals Using CFD to Evaluate Natural Ventilation through a 3D Parametric Modeling Approach

Energies ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2197
Author(s):  
Nayara Rodrigues Marques Sakiyama ◽  
Jurgen Frick ◽  
Timea Bejat ◽  
Harald Garrecht
Keyword(s):  
Natural Ventilation ◽  
Parametric Modeling ◽  
Cfd Simulations ◽  
3D Design ◽  
Post Process ◽  
Test House ◽  
Model Set ◽  
Computational Fluid Dynamics Cfd ◽  
Set Up ◽  
Passive Strategy

Predicting building air change rates is a challenge for designers seeking to deal with natural ventilation, a more and more popular passive strategy. Among the methods available for this task, computational fluid dynamics (CFD) appears the most compelling, in ascending use. However, CFD simulations require a range of settings and skills that inhibit its wide application. With the primary goal of providing a pragmatic CFD application to promote wind-driven ventilation assessments at the design phase, this paper presents a study that investigates natural ventilation integrating 3D parametric modeling and CFD. From pre- to post-processing, the workflow addresses all simulation steps: geometry and weather definition, including incident wind directions, a model set up, control, results’ edition, and visualization. Both indoor air velocities and air change rates (ACH) were calculated within the procedure, which used a test house and air measurements as a reference. The study explores alternatives in the 3D design platform’s frame to display and compute ACH and parametrically generate surfaces where air velocities are computed. The paper also discusses the effectiveness of the reference building’s natural ventilation by analyzing the CFD outputs. The proposed approach assists the practical use of CFD by designers, providing detailed information about the numerical model, as well as enabling the means to generate the cases, visualize, and post-process the results.

scholarly journals Dependence of the Flue Gas Flow on the Setting of the Separation Baffle in the Flue Gas Tract

2021 ◽  
Vol 11 (7) ◽  
pp. 2961
Author(s):  
Nikola Čajová Kantová ◽  
Alexander Čaja ◽  
Marek Patsch ◽  
Michal Holubčík ◽  
Peter Ďurčanský
Keyword(s):  
Particulate Matter ◽  
Flue Gas ◽  
Gas Flow ◽  
Negative Impact ◽  
Combustion Process ◽  
Cfd Simulations ◽  
Piv Measurements ◽  
Computational Fluid Dynamics Cfd ◽  
Particle Imaging ◽  
Combustion Of Solid Fuels

With the combustion of solid fuels, emissions such as particulate matter are also formed, which have a negative impact on human health. Reducing their amount in the air can be achieved by optimizing the combustion process as well as the flue gas flow. This article aims to optimize the flue gas tract using separation baffles. This design can make it possible to capture particulate matter by using three baffles and prevent it from escaping into the air in the flue gas. The geometric parameters of the first baffle were changed twice more. The dependence of the flue gas flow on the baffles was first observed by computational fluid dynamics (CFD) simulations and subsequently verified by the particle imaging velocimetry (PIV) method. Based on the CFD results, the most effective is setting 1 with the same boundary conditions as those during experimental PIV measurements. Setting 2 can capture 1.8% less particles and setting 3 can capture 0.6% less particles than setting 1. Based on the stoichiometric calculations, it would be possible to capture up to 62.3% of the particles in setting 1. The velocities comparison obtained from CFD and PIV confirmed the supposed character of the turbulent flow with vortexes appearing in the flue gas tract, despite some inaccuracies.

Large-Scale Simulation of the Clocking Impact of 2D Combustor Profile on a Two Stage High Pressure Turbine

2014 ◽  
Author(s):  
Thomas E. Dyson ◽  
David B. Helmer ◽  
James A. Tallman
Keyword(s):  
High Pressure ◽  
Large Scale ◽  
High Pressure Turbine ◽  
Cfd Simulations ◽  
Two Stage ◽  
Substantial Impact ◽  
Sliding Mesh ◽  
Wall Flow ◽  
End Wall ◽  
Film Flows

This paper presents sliding-mesh unsteady CFD simulations of high-pressure turbine sections of a modern aviation engine in an extension of previously presented work [1]. The simulation included both the first and second stages of a two-stage high-pressure turbine. Half-wheel domains were used, with source terms representing purge and film flows. The end-wall flow-path cavities were incorporated in the domain to a limited extent. The passage-to-passage variation in thermal predictions was compared for a 1D and 2D turbine inlet boundary condition. Substantial impact was observed on both first and second stage vanes despite the mixing from the first stage blade. Qualitative and quantitative differences in surface temperature distributions were observed due to different ratios between airfoil counts in the two domains.

scholarly journals Investigations of Inducers Operating With High Rotational Speed

2018 ◽  
Vol 141 (4) ◽  
Author(s):  
Björn Gwiasda ◽  
Matthias Mohr ◽  
Martin Böhle
Keyword(s):  
Rotational Speed ◽  
Test Bench ◽  
Pressure Rise ◽  
Working Fluid ◽  
Cfd Simulations ◽  
High Rotational Speed ◽  
Rotating Speed ◽  
Performance Pressure ◽  
Computational Fluid Dynamics Cfd ◽  
Suction Performance

Suction performance, pressure rise, and efficiency for four different inducers are examined with computational fluid dynamics (CFD) simulations and experiments performed with 18,000 rpm and 24,000 rpm. The studies originate from a research project that includes the construction of a new test bench in order to judge the design of the different inducers. This test bench allows to conduct experiments with a rotational speed of up to 40,000 rpm and high pressure ranges from 0.1 bar to 40 bar with water as working fluid. Experimental results are used to evaluate the accuracy of the simulations and to gain a better understanding of the design parameter. The influence of increasing the rotating speed from 18,000 rpm to 24,000 rpm on the performance is also shown.

scholarly journals Rapid pivot feeding in pipefish: flow effects on prey and evaluation of simple dynamic modelling via computational fluid dynamics

2008 ◽  
Vol 5 (28) ◽  
pp. 1291-1301 ◽  
Author(s):  
Sam Van Wassenbergh ◽  
Peter Aerts
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Analytical Model ◽  
Dynamic Modelling ◽  
Head Rotation ◽  
Theoretical Models ◽  
Cfd Simulations ◽  
Deceleration Phase ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Effects

Most theoretical models of unsteady aquatic movement in organisms assume that including steady-state drag force and added mass approximates the hydrodynamic force exerted on an organism's body. However, animals often perform explosively quick movements where high accelerations are realized in a few milliseconds and are followed closely by rapid decelerations. For such highly unsteady movements, the accuracy of this modelling approach may be limited. This type of movement can be found during pivot feeding in pipefish that abruptly rotate their head and snout towards prey. We used computational fluid dynamics (CFD) to validate a simple analytical model of cranial rotation in pipefish. CFD simulations also allowed us to assess prey displacement by head rotation. CFD showed that the analytical model accurately calculates the forces exerted on the pipefish. Although the initial phase of acceleration changes the flow patterns during the subsequent deceleration phase, the accuracy of the analytical model was not reduced during this deceleration phase. Our analysis also showed that prey are left approximately stationary despite the quickly approaching pipefish snout. This suggests that pivot-feeding fish need little or no suction to compensate for the effects of the flow induced by cranial rotation.

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