scholarly journals Static Analysis of Unsteady Aerodynamics Wake of Simplified Helicopter Model Via Simulation Work

2021 ◽  
Vol 89 (1) ◽  
pp. 142-153
Author(s):  
Nurain Othman ◽  
Iskandar Shah Ishak ◽  
Md. Nizam Dahalan
Keyword(s):  
Total Pressure ◽  
Research Work ◽  
Three Dimensional ◽  
Unsteady Aerodynamics ◽  
Simplified Model ◽  
Computational Domain ◽  
Complex Flow ◽  
Computational Tools ◽  
Model Helicopter ◽  
Interaction Phenomena

Computational tools have led and helped researchers in providing advanced results, notably in rotorcraft research, as flow around the helicopter is dominated by complex aerodynamics and flow interaction phenomena. This research work aimed to evaluate the aerodynamic computational results on a simplified model helicopter when the model was subjected to the angles of attack 0°, -5°, -15°, and -20°, respectively. The study also examined the unsteady flow behaviour on the three-dimensional elliptical shape of a fuselage equipped with a rotor hub of the single rotor blade. The computational domain for the aerodynamic flow field was created within the size of 7 m (length) x 5 m (width) x 5 m (height). Results showed that an increase in the angle of attack in the rotor component caused additional drag of about 34% to 45% whilst the fuselage component contributed about 55% to 65% to drag increment. Also, a significant value of total pressure from -235 Pa to 250 Pa demonstrated along the simplified model helicopter distinctly showed that the complexity of geometry caused adverse pressure. The findings of this research work could potentially improve the understanding of complex flow surrounding the helicopter that has always baffled the aerodynamicists.

scholarly journals Cold Flow Computations for the Diffuser-Combustor Section of an Industrial Gas Turbine

1996 ◽  
Author(s):  
Dadong Zhou ◽  
Ting Wang ◽  
William R. Ryan
Keyword(s):  
Gas Turbine ◽  
Total Pressure ◽  
Reverse Flow ◽  
Three Dimensional ◽  
Complex Flow ◽  
Pressure Losses ◽  
Structured Grid ◽  
Computational Fluid Dynamics Cfd ◽  
Enhance Efficiency ◽  
Industrial Gas Turbine

In the first part of a multipart project to analyze and optimize the complex three-dimensional diffuser-combustor section of a highly advanced industrial gas turbine under development, a computational fluid dynamics (CFD) analysts has been conducted. The commercial FEA code I-DEAS was used to complete the three-dimensional solid modeling and the structured grid generation. The flow calculation was conducted using the commercial CFD code PHOENICS. The multiblock method was employed to enhance computational capabilities. The mechanisms of the total pressure losses and possible ways to enhance efficiency by reducing the total pressure losses were examined. Mechanisms that contribute to the nonuniform velocity distribution of flow entering the combustor were also identified. The CFD results were informative and provided insight to the complex flow patterns in the reverse flow dump diffuser, however, the results are qualitative and are useful primarily as guidelines for optimization as opposed to firm design configuration selections.

Impact of a Collector Box on the Pressure Recovery of an Exhaust Diffuser System

2011 ◽  
Author(s):  
Bryan C. Bernier ◽  
Mark Ricklick ◽  
J. S. Kapat
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Experimental Tests ◽  
Total Pressure Loss ◽  
Pressure Recovery ◽  
Computational Domain ◽  
Complex Flow ◽  
Local Pressure ◽  
3 Dimensional ◽  
Pressure Profiles

The effects of an industrial gas turbine’s Exhaust Collector Box (ECB) geometry on static pressure recovery and total pressure loss were investigated in this study. This study aims to further understand how exit boundary conditions affect the performance of a diffuser system. In this investigation, the exhaust diffuser remained constant through each test, with collector box geometries being varied. The same uniform velocity profile was maintained at the diffuser inlet for all geometries considered. The local pressure recovery through the diffuser with 4 axial ports at 4 circumferential locations was reported along with 14 locations in the accompanying ECB. A system performance analysis for each geometry was conducted using the total pressure loss from inlet to exit of the model. Velocity and total pressure profiles obtained with a hotwire anemometer and Kiel probe at the exit of the diffuser and at the exit of the ECB are also presented in this study. Three (3) different ECB geometries are investigated at a Reynolds number of 60,000. Results obtained from these experimental tests are used to validate the accuracy of a 3-dimensional RANS with realizable k-ε turbulence CFD model from the commercial software package Star-CCM+. The study confirms the existence of two strong counter-rotating helical vortices at the exit of the ECB which significantly affect the flow within the diffuser. Evidence of a strong recirculation zone within the ECB was found to force separation within the exhaust diffuser. Extending the length of the ECB proved to decrease the total pressure loss of the system by up to 19% experimentally. Additionally, the realizable k-ε turbulence was able to accurately represent the total pressure loss of the system within 5%. Despite the extremely complex flow field within the ECB, the computational domain reasonably represented the system in both magnitude and trends.

Computation of Ingestion Through Gas Turbine Rim Seals

2011 ◽  
Author(s):  
Kunyuan Zhou ◽  
Mike Wilson ◽  
J. Michael Owen ◽  
Gary Lock
Keyword(s):  
Pressure Distribution ◽  
Flow Rate ◽  
Pressure Difference ◽  
Computational Models ◽  
Three Dimensional ◽  
Rotor Blades ◽  
Driving Mechanism ◽  
Computational Domain ◽  
Complex Flow ◽  
Rotating Blade

Three-dimensional unsteady computational fluid dynamics (CFD) is applied to the ingestion of fluid from a non-uniform mainstream annulus flow via a rim-seal into a rotor-stator wheel-space. The results provide understanding of the complex flow and information for the development of more efficient computational models and analytical ‘orifice models’. The commercial CFD code CFX has been used to carry out unsteady RANS computations with an SST turbulence model. A scalar equation is employed to represent the seeded tracer gas that can be used in experiments to determine sealing effectiveness, and the variation of effectiveness with sealing flow rate is determined for a simple axial clearance seal and one combination of axial and rotational Reynolds numbers. The computational domain comprises one pitch in a row of stator vanes and rotor blades The rotating blade is accounted for by a sliding interface between the stationary and rotating sections of the model, located downstream of the seal clearance. The unsteady computations confirm that the magnitude of the peak-to-trough pressure difference in the annulus is the principal driving mechanism for ingestion (or ingress) into the wheel-space. This pressure difference is used in orifice models to predict sealing effectiveness; its magnitude however depends on the locations in the annulus and the wheel-space that are chosen for its evaluation as well as the sealing flow rate. The CFD is used to investigate the appropriateness of the locations that are often used to determine the pressure difference. It is shown that maximum ingestion occurs when the static pressure peak produced by the vane combines with that produced by the blade, and that highly swirled ingrested flow could contact both the stator and rotor disk when little sealing flow is provided. The relationships between the unsteady simulations and simplified, more computationally efficient steady computations are also investigated. For the system considered here, ingress is found to be dictated principally by the pressure distribution caused by the vane. The effect of the rotating blade on the pressure distribution in the annulus is investigated by comparing the unsteady results with those for steady models that do not involve a blade. It is found that the presence of the blade increases the pressure asymmetry in the annulus. Although the pressure asymmetry predicted by unsteady and steady models have a similar magnitude, the sealing effectiveness is over-predicted considerably for the corresponding steady model. If a “thin seal” geometric approximation is used in the steady model, however, similar effectiveness results compared with the unsteady model may be obtained much more economically.

Conceptual Design of an Adaptive Wind Tunnel for the Generation of Unsteady Complex Flow Patterns

2005 ◽  
Author(s):  
Richard Kirkman ◽  
Meredith Metzger
Keyword(s):  
Wind Tunnel ◽  
Virtual Environments ◽  
Conceptual Design ◽  
Three Dimensional ◽  
Unsteady Aerodynamics ◽  
Mesh Size ◽  
Flow Patterns ◽  
Complex Flow ◽  
Tunnel Design ◽  
Wind Tunnel Design

The present paper describes the conceptual design of a three-dimensional adaptive wind tunnel capable of generating complex, unsteady flow fields in a relatively compact physical domain. The design involves multiple, independently controllable vents located around the periphery of a semi-enclosed facility. Desired flow patterns at target areas within the facility are produced by actively steering the inlet flow via appropriately adjusting the magnitude and direction of the air flow entering from each vent. The present study is motivated by a desire to incorporate tactile wind sensation into CAVE-like virtual environments, thereby increasing the overall sense of immersion in the virtual reality. The present wind tunnel design concept may also have potential application to laboratory studies of such problems as unsteady aerodynamics. Results in the present study include examples of two flow patterns obtained from numerical simulations using Fluent. Results from a companion parametric study analyzing the sensitivity of the numerical solution to mesh size and tolerance are also provided. In addition, the feasibility of using a linear-based control strategy to generate prescribed flow patterns within the wind tunnel is discussed.

Effect of Blade Profile Contouring on Endwall Flow Structure in a High-Lift Low-Pressure Turbine Cascade

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
Keith Sangston ◽  
Jesse Little ◽  
M. Eric Lyall ◽  
Rolf Sondergaard
Keyword(s):  
Total Pressure ◽  
Three Dimensional ◽  
Low Pressure ◽  
Stereoscopic Particle Image Velocimetry ◽  
Loss Reduction ◽  
Mean Flow ◽  
High Lift ◽  
Computational Tools ◽  
Design Modification ◽  
Low Pressure Turbine

Previous work has shown that low-stagger contouring near the endwall of a nominally high-lift and high-stagger angle front-loaded low-pressure turbine (LPT) airfoil is successful in reducing endwall loss by limiting the development and migration of low momentum fluid associated with secondary flow structures. The design modification that leads to loss reduction in that study was determined from an intuitive approach based on the premise that reducing flow separation near the endwall will lead to reduced loss production. Those authors also relied heavily upon Reynolds-averaged Navier–Stokes (RANS) based computational tools. Due to uncertainties inherent in computational fluid dynamics (CFD) predictions, there is little confidence that the authors actually achieved true minimum loss. Despite recent advances in computing capability, turbulence modeling remains a shortcoming of modern design tools. As a contribution to overcoming this problem, this paper offers a three-dimensional (3D) view of the developing mean flow, total pressure, and turbulence fields that gave rise to the loss reduction of the airfoil mentioned above. Experiments are conducted in a linear cascade with aspect ratio of 3.5 and Re = 100,000. The results are derived from stereoscopic particle image velocimetry (PIV) and total pressure measurements inside the passage. Overall, the loss reduction correlates strongly with reduced turbulence production. The aim of this paper is to provide readers with a realistic view of mean flow and turbulence development that include all the components of the Reynolds stress tensor to assess, at least qualitatively, the validity of high fidelity computational tools used to calculate turbine flows.

A Study of Fan-Distortion Interaction Within the NASA Rotor 67 Transonic Stage

2010 ◽  
Author(s):  
V. Jerez Fidalgo ◽  
C. A. Hall ◽  
Y. Colin
Keyword(s):  
Total Pressure ◽  
Three Dimensional ◽  
Measurement Data ◽  
Test Case ◽  
Complex Flow ◽  
Inlet Flow ◽  
Flow Features ◽  
Work Input ◽  
Flow Effects ◽  
Transonic Fan

The performance of a transonic fan operating within non-uniform inlet flow remains a key concern for the design and operability of a turbofan engine. This paper applies computational methods to improve the understanding of the interaction between a transonic fan and an inlet total pressure distortion. The test case studied is the NASA rotor 67 stage operating with a total pressure distortion covering a 120-degree sector of the inlet flow-field. Full-annulus, unsteady, three-dimensional CFD has been used to simulate the test rig installation and the full fan assembly operating with inlet distortion. Novel post-processing methods have been applied to extract the fan performance and features of the interaction between the fan and the non-uniform inflow. The results of the unsteady computations agree well with the measurement data. The local operating condition of the fan at different positions around the annulus has been tracked and analysed, and this is shown to be highly dependent on the swirl and mass flow redistribution that the rotor induces ahead of it due to the incoming distortion. The upstream flow effects lead to a variation in work input that determines the distortion pattern seen downstream of the fan stage. In addition, the unsteady computations also reveal more complex flow-features downstream of the fan stage, which arise due to the three-dimensionality of the flow and unsteadiness.

A Study of Fan-Distortion Interaction Within the NASA Rotor 67 Transonic Stage

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
V. Jerez Fidalgo ◽  
C. A. Hall ◽  
Y. Colin
Keyword(s):  
Total Pressure ◽  
Three Dimensional ◽  
Measurement Data ◽  
Test Case ◽  
Complex Flow ◽  
Inlet Flow ◽  
Flow Features ◽  
Work Input ◽  
Flow Effects ◽  
Transonic Fan

The performance of a transonic fan operating within nonuniform inlet flow remains a key concern for the design and operability of a turbofan engine. This paper applies computational methods to improve the understanding of the interaction between a transonic fan and an inlet total pressure distortion. The test case studied is the NASA rotor 67 stage operating with a total pressure distortion covering a 120-deg sector of the inlet flow field. Full-annulus, unsteady, three-dimensional CFD has been used to simulate the test rig installation and the full fan assembly operating with inlet distortion. Novel post-processing methods have been applied to extract the fan performance and features of the interaction between the fan and the nonuniform inflow. The results of the unsteady computations agree well with the measurement data. The local operating condition of the fan at different positions around the annulus has been tracked and analyzed, and this is shown to be highly dependent on the swirl and mass flow redistribution that the rotor induces ahead of it due to the incoming distortion. The upstream flow effects lead to a variation in work input that determines the distortion pattern seen downstream of the fan stage. In addition, the unsteady computations also reveal more complex flow features downstream of the fan stage, which arise due to the three dimensionality of the flow and unsteadiness.

Numerical investigations on the effect of volute casing treatment for performance augmentation in a centrifugal fan

2021 ◽  
pp. 095440622110341
Author(s):  
Manjunath L Nilugal ◽  
K Vasudeva Karanth ◽  
Madhwesh N
Keyword(s):  
Total Pressure ◽  
Static Pressure ◽  
Numerical Study ◽  
Pressure Coefficient ◽  
Three Dimensional ◽  
Pressure Rise ◽  
Centrifugal Fan ◽  
Casing Treatment ◽  
Sliding Mesh ◽  
Optimum Configuration

This article presents the effect of volute chamfering on the performance of a forward swept centrifugal fan. The numerical analysis is performed to obtain the performance parameters such as static pressure rise coefficient and total pressure coefficient for various flow coefficients. The chamfer ratio for the volute is optimized parametrically by providing a chamfer on either side of the volute. The influence of the chamfer ratio on the three dimensional flow domain was investigated numerically. The simulation is carried out using Re-Normalisation Group (RNG) k-[Formula: see text] turbulence model. The transient simulation of the fan system is done using standard sliding mesh method available in Fluent. It is found from the analysis that, configuration with chamfer ratio of 4.4 is found be the optimum configuration in terms of better performance characteristics. On an average, this optimum configuration provides improvement of about 6.3% in static pressure rise coefficient when compared to the base model. This optimized chamfer configuration also gives a higher total pressure coefficient of about 3% validating the augmentation in static pressure rise coefficient with respect to the base model. Hence, this numerical study establishes the effectiveness of optimally providing volute chamfer on the overall performance improvement of forward bladed centrifugal fan.

scholarly journals Data-Informed Decomposition for Localized Uncertainty Quantification of Dynamical Systems

Vibration ◽  
2020 ◽  
Vol 4 (1) ◽  
pp. 49-63
Author(s):  
Waad Subber ◽  
Sayan Ghosh ◽  
Piyush Pandita ◽  
Yiming Zhang ◽  
Liping Wang
Keyword(s):  
Dynamical Systems ◽  
Computational Cost ◽  
Three Dimensional ◽  
Region Of Interest ◽  
System Response ◽  
Computational Domain ◽  
User Interest ◽  
Numerical Resolution ◽  
Multi Scale ◽  
Operation Conditions

Industrial dynamical systems often exhibit multi-scale responses due to material heterogeneity and complex operation conditions. The smallest length-scale of the systems dynamics controls the numerical resolution required to resolve the embedded physics. In practice however, high numerical resolution is only required in a confined region of the domain where fast dynamics or localized material variability is exhibited, whereas a coarser discretization can be sufficient in the rest majority of the domain. Partitioning the complex dynamical system into smaller easier-to-solve problems based on the localized dynamics and material variability can reduce the overall computational cost. The region of interest can be specified based on the localized features of the solution, user interest, and correlation length of the material properties. For problems where a region of interest is not evident, Bayesian inference can provide a feasible solution. In this work, we employ a Bayesian framework to update the prior knowledge of the localized region of interest using measurements of the system response. Once, the region of interest is identified, the localized uncertainty is propagate forward through the computational domain. We demonstrate our framework using numerical experiments on a three-dimensional elastodynamic problem.

Numerical study of multi-dimensional hyperbolic telegraph equations arising in nuclear material science via an efficient local meshless method

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Imtiaz Ahmad ◽  
Aly R. Seadawy ◽  
Hijaz Ahmad ◽  
Phatiphat Thounthong ◽  
Fuzhang Wang
Keyword(s):  
Meshless Method ◽  
Material Science ◽  
Numerical Study ◽  
Research Work ◽  
Time Integration ◽  
Three Dimensional ◽  
Nuclear Material ◽  
Telegraph Equations ◽  
Model Equations ◽  
Derivatives Of

Abstract This research work is to study the numerical solution of three-dimensional second-order hyperbolic telegraph equations using an efficient local meshless method based on radial basis function (RBF). The model equations are used in nuclear material science and in the modeling of vibrations of structures. The explicit time integration technique is utilized to semi-discretize the model in the time direction whereas the space derivatives of the model are discretized by the proposed local meshless procedure based on multiquadric RBF. Numerical experiments are performed with the proposed numerical scheme for rectangular and non-rectangular computational domains. The proposed method solutions are converging quickly in comparison with the different existing numerical methods in the recent literature.

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