Design of a rotor blade tip for the investigation of dynamic stall in the transonic wind-tunnel Göttingen

2016 ◽  
Vol 120 (1232) ◽  
pp. 1509-1533 ◽  
Author(s):  
B. Lütke ◽  
J. Nuhn ◽  
Y. Govers ◽  
M. Schmidt
Keyword(s):  
Experimental Data ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Numerical Data ◽  
Dynamic Stall ◽  
Navier Stokes ◽  
Fe Model ◽  
Stress Distributions ◽  
Cfd Simulations ◽  
Blade Tip

ABSTRACTThe aerodynamic and structural design of a pitching blade tip with a double-swept planform is presented. The authors demonstrate how high-fidelity finite element (FE) and computational fluid dynamic (CFD) simulations are successfully used in the design phase. Eigenfrequencies, deformation, and stress distributions are evaluated by means of a three-dimensional (3D) FE model. Unsteady Reynolds-averaged Navier-Stokes (RANS) simulations are compared to experimental data for a light dynamic stall case atMa= 0.5,Re= 1.2 × 106. The results show a very good agreement as long as the flow stays attached. Tendencies for the span-wise location of separation are captured. As soon as separation sets in, discrepancies between experimental and numerical data are observed. The experimental data show that for light dynamic stall cases atMa= 0.5, a factor of safety ofFoS= 2.0 is sufficient if the presented simulation methods are used.

Reducing the Effects of Blast to the Head Through Load Partitioning

2013 ◽  
Author(s):  
Mark A. Rapo ◽  
Tim Baumer ◽  
Philemon C. Chan ◽  
James F. MacKiewicz
Keyword(s):  
Fluid Dynamic ◽  
Three Dimensional ◽  
Pressure Sensors ◽  
Field Tests ◽  
Navier Stokes ◽  
Head Acceleration ◽  
Cfd Simulations ◽  
Blast Overpressure ◽  
Head Protection ◽  
Size Standard

Warfighters who survive encounters with improvised explosive devices (IEDs) may incur mild traumatic brain injury (mTBI) due to blast overpressure effects. Since existing head injury criteria are mostly based on head kinematics, head acceleration is one key metric to be measured. A blast wave travels at supersonic speed with a very sharp peak overpressure rise followed by a rapid decay within a short duration. For the surface area that is covered by the helmet, the cushion/suspension subsystem is responsible for mitigating the blast effects on the head, while the exposed area of the head or face would receive a direct blast loading. Computational fluid dynamic (CFD) simulations of a blast on an upright warfighter show a significant reduction in peak force to the head when a helmet is worn. For a helmet with an attached eye-shield, the load to the head from a front blast can be reduced further. A field study was conducted to verify that the increased load partitioned away from face and to the helmet and cushioning system would result in decreased head acceleration. Blast field tests were conducted using 4 lbs. of cylindrical C4 charges at 92″ standoff. Head acceleration was measured using combinations of a free hanging mid-size standard ISO headform fitted with Team Wendy (TW) pads, an advanced combat helmet (ACH), and an eye-shield. Tests were performed with the blast hitting the front, side and back of the helmeted headform system. Headform accelerations ranging from 120–465g were recorded based on blast direction and the amount of head protection. To validate the three-dimensional Navier-Stokes’ based CFD simulations, a custom-designed blast overpressure bust (BOB) containing 22 surface pressure sensors was mounted on top of the BTD to measure the pressure distribution over the head and face when exposed to a blast. The incident overpressure of the blast was 0.25MPa, with reflected pressures reaching 1.0MPa.

The inlet flow structure of a conceptual open-nose supersonic drone

2021 ◽  
pp. 095441002098304
Author(s):  
Eiman B Saheby ◽  
Xing Shen ◽  
Anthony P Hays ◽  
Zhang Jun
Keyword(s):  
Flow Structure ◽  
Stokes Equations ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Computational Fluid Dynamic Simulation ◽  
Navier Stokes ◽  
Ansys Fluent ◽  
Navier Stokes Equations ◽  
Aerodynamic Efficiency ◽  
Performance Effects

This study describes the aerodynamic efficiency of a forebody–inlet configuration and computational investigation of a drone system, capable of sustainable supersonic cruising at Mach 1.60. Because the whole drone configuration is formed around the induction system and the design is highly interrelated to the flow structure of forebody and inlet efficiency, analysis of this section and understanding its flow pattern is necessary before any progress in design phases. The compression surface is designed analytically using oblique shock patterns, which results in a low drag forebody. To study the concept, two inlet–forebody geometries are considered for Computational Fluid Dynamic simulation using ANSYS Fluent code. The supersonic and subsonic performance, effects of angle of attack, sideslip, and duct geometries on the propulsive efficiency of the concept are studied by solving the three-dimensional Navier–Stokes equations in structured cell domains. Comparing the results with the available data from other sources indicates that the aerodynamic efficiency of the concept is acceptable at supersonic and transonic regimes.

scholarly journals Computational Analysis to Factor Wind into the Design of an Architectural Environment

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Hassam Nasarullah Chaudhry ◽  
John Kaiser Calautit ◽  
Ben Richard Hughes
Keyword(s):  
Fluid Dynamics ◽  
Power Generation ◽  
Computational Fluid Dynamics ◽  
Three Dimensional ◽  
Numerical Data ◽  
Navier Stokes ◽  
Windward Side ◽  
Average Value ◽  
Continuity Equations ◽  
Prevailing Wind Direction

The effect of wind distribution on the architectural domain of the Bahrain Trade Centre was numerically analysed using computational fluid dynamics (CFD). Using the numerical data, the power generation potential of the building-integrated wind turbines was determined in response to the prevailing wind direction. The three-dimensional Reynolds-averaged Navier-Stokes (RANS) equations along with the momentum and continuity equations were solved for obtaining the velocity and pressure field. Simulating a reference wind speed of 6 m/s, the findings from the study quantified an estimate power generation of 6.4 kW indicating a capacity factor of 2.9% for the benchmark model. At the windward side of the building, it was observed that the layers of turbulence intensified in inverse proportion to the height of the building with an average value of 0.45 J/kg. The air velocity was found to gradually increase in direct proportion to the elevation with the turbine located at higher altitude receiving maximum exposure to incoming wind. This work highlighted the potential of using advanced computational fluid dynamics in order to factor wind into the design of any architectural environment.

Forced Response Variation of Aerodynamically and Structurally Mistuned Turbo-Machinery Rotors

2006 ◽  
Author(s):  
I. Sladojevic´ ◽  
E. P. Petrov ◽  
M. Imregun ◽  
A. I. Sayma
Keyword(s):  
Three Dimensional ◽  
Forced Response ◽  
Navier Stokes ◽  
Fe Model ◽  
Frequency Shifts ◽  
Aero Engine ◽  
Different Types ◽  
Aerodynamic Parameters ◽  
Reynolds Averaged Navier Stokes ◽  
Response Variation

The paper presents the results of a study looking into changes in the forced response levels of bladed disc assemblies subject to both structural and aerodynamic mistuning. A whole annulus FE model, representative of a civil aero-engine fan with 26 blades was used in the calculations. The forced response of all blades of 1000 random mistuned patterns was calculated. The aerodynamic parameters, frequency shifts and damping, were calculated using a three-dimensional Reynolds-averaged Navier-Stokes aero-elasticity code. They were randomly varied for each mistuning pattern, with the assumption that the system would remain stable, i.e. flutter would not occur due to aerodynamic mistuning. The results show the variation of the forced response with different types of mistuning, with structural mistuning only, with aerodynamic mistuning only and with both structural and aerodynamic mistuning.

Effects of Tip Clearance on Hot Streak Migration in a High-Subsonic Single-Stage Turbine

2000 ◽  
Author(s):  
Daniel J. Dorney ◽  
Douglas L. Sondak
Keyword(s):  
Experimental Data ◽  
Three Dimensional ◽  
Single Stage ◽  
Rotor Blades ◽  
Tip Clearance ◽  
Navier Stokes ◽  
Radial Spreading ◽  
Rotor Surface ◽  
Hot Streak ◽  
Turbine Airfoils

Experimental data have shown that combustor temperature non-uniformities can lead to the excessive heating of first-stage rotor blades in turbines. This heating of the rotor blades can lead to thermal fatigue and degrade turbine performance. The results of recent studies have shown that variations in the circumferential location, or clocking, of the first-stage vane airfoils can be used to minimize the adverse effects of the hot streaks due to the hot fluid mixing with the cooler fluid contained in the vane wake. In addition, the effects of the hot streak/airfoil count ratio on the heating patterns of turbine airfoils have been quantified. In the present investigation, three-dimensional unsteady Navier-Stokes simulations have been performed for a single-stage high-pressure turbine geometry operating in high subsonic flow to study the effects of tip clearance on hot streak migration. Baseline simulations were initially performed without hot streaks to compare with the experimental data. Two simulations were then performed with a superimposed combustor hot streak; in the first the tip clearance was set at the experimental value, while in the second the rotor was allowed to scrape along the outer case (i.e., the limit as the tip clearance goes to zero). The predicted results for the baseline simulations show good agreement with the available experimental data. The simulations with the hot streak indicate that the tip clearance increases the radial spreading of the hot fluid, and increases the integrated rotor surface temperature compared to the case without tip clearance.

A Calculation Scheme for Three-Dimensional Viscous Incompressible Flows

1987 ◽  
Vol 109 (4) ◽  
pp. 345-352 ◽  
Author(s):  
M. Reggio ◽  
R. Camarero
Keyword(s):  
Incompressible Flows ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Numerical Procedure ◽  
Numerical Data ◽  
Momentum Balance ◽  
Navier Stokes ◽  
Test Cases ◽  
Pressure Gradients ◽  
Navier Stokes Equations

A numerical procedure to solve three-dimensional incompressible flows in arbitrary shapes is presented. The conservative form of the primitive-variable formulation of the time-dependent Navier-Stokes equations written for a general curvilinear coordiante system is adopted. The numerical scheme is based on an overlapping grid combined with opposed differencing for mass and pressure gradients. The pressure and the velocity components are stored at the same location: the center of the computational cell which is used for both mass and the momentum balance. The resulting scheme is stable and no oscillations in the velocity or pressure fields are detected. The method is applied to test cases of ducting and the results are compared with experimental and numerical data.

Three-Dimensional Navier-Stokes Analysis of Turbine Rotor and Tip-Leakage Flowfield

1997 ◽  
Author(s):  
J. Luo ◽  
B. Lakshminarayana
Keyword(s):  
Three Dimensional ◽  
Turbine Rotor ◽  
Secondary Flows ◽  
Tip Clearance ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Mean Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Blade Tip

The 3-D viscous flowfield in the rotor passage of a single-stage turbine, including the tip-leakage flow, is computed using a Navier-Stokes procedure. A grid-generation code has been developed to obtain embedded H grids inside the rotor tip gap. The blade tip geometry is accurately modeled without any “pinching”. Chien’s low-Reynolds-number k-ε model is employed for turbulence closure. Both the mean-flow and turbulence transport equations are integrated in time using a four-stage Runge-Kutta scheme. The computational results for the entire turbine rotor flow, particularly the tip-leakage flow and the secondary flows, are interpreted and compared with available data. The predictions for major features of the flowfield are found to be in good agreement with the data. Complicated interactions between the tip-clearance flows and the secondary flows are examined in detail. The effects of endwall rotation on the development and interaction of secondary and tip-leakage vortices are also analyzed.

Numerical 3-D Conjugated Heat Transfer Simulation of a First Inter-Stage Internal Cooled Thermal Barrier Coated Gas Turbine Bucket

2007 ◽  
Author(s):  
Alejandro Herna´ndez Rossette ◽  
Zdzislaw Mazur C. ◽  
Jesu´s Cordero Guridi ◽  
Eric Chumacero Polanco
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Thermal Loading ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Thermal Barrier ◽  
Cfd Simulations ◽  
Temperature Changes ◽  
Heat Transfer Simulation ◽  
Conjugated Heat Transfer

As a gas turbine entry temperature (TET) increases, thermal loading on first stage blades increases too and therefore, a variety of cooling techniques and thermal barrier coatings (TBCs) are used to maintain the blade temperature within the acceptable limits. In this work a multi-block three dimensional Navier-Stokes commercial turbomachinery oriented CFD-code has been used to compute steady state conjugated heat transfer (CHT) on the blade suction and pressure coated sides of a rotating first inter-stage (nozzle and bucket) with cooling holes of a 60 MW Gas turbine. A Spallart Allmaras model was used for modeling the turbulence. Convection and radiation were modeled for a super alloy blade with and without TBC. The CFD simulations were configured with a mesh domain of nozzle and bucket inter-stage in order to predict the fluid parameters at inlet and outlet of bucket for validate with turbine inter-stage parameter data test of gas turbine manufacturer. The effects of blade surface temperature changes were simulated with both configurations coated and uncoated blades.

Computational Fluid Dynamics Modeling of Mixed Convection Flows in Building Enclosures

2013 ◽  
Author(s):  
Alexander Kayne ◽  
Ramesh Agarwal
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Experimental Data ◽  
Computational Fluid Dynamics ◽  
Mixed Convection ◽  
Turbulence Model ◽  
Numerical Algorithm ◽  
Navier Stokes ◽  
Cfd Simulations ◽  
Flow And Heat Transfer

In recent years Computational Fluid Dynamics (CFD) simulations are increasingly used to model the air circulation and temperature environment inside the rooms of residential and office buildings to gain insight into the relative energy consumptions of various HVAC systems for cooling/heating for climate control and thermal comfort. This requires accurate simulation of turbulent flow and heat transfer for various types of ventilation systems using the Reynolds-Averaged Navier-Stokes (RANS) equations of fluid dynamics. Large Eddy Simulation (LES) or Direct Numerical Simulation (DNS) of Navier-Stokes equations is computationally intensive and expensive for simulations of this kind. As a result, vast majority of CFD simulations employ RANS equations in conjunction with a turbulence model. In order to assess the modeling requirements (mesh, numerical algorithm, turbulence model etc.) for accurate simulations, it is critical to validate the calculations against the experimental data. For this purpose, we use three well known benchmark validation cases, one for natural convection in 2D closed vertical cavity, second for forced convection in a 2D rectangular cavity and the third for mixed convection in a 2D square cavity. The simulations are performed on a number of meshes of different density using a number of turbulence models. It is found that k-epsilon two-equation turbulence model with a second-order algorithm on a reasonable mesh gives the best results. This information is then used to determine the modeling requirements (mesh, numerical algorithm, turbulence model etc.) for flows in 3D enclosures with different ventilation systems. In particular two cases are considered for which the experimental data is available. These cases are (1) air flow and heat transfer in a naturally ventilated room and (2) airflow and temperature distribution in an atrium. Good agreement with the experimental data and computations of other investigators is obtained.

scholarly journals Three-Dimensional Turbulent Vortex Shedding From a Surface-Mounted Square Cylinder: Predictions With Large-Eddy Simulations and URANS

2014 ◽  
Vol 136 (6) ◽  
Author(s):  
B. A. Younis ◽  
A. Abrishamchi
Keyword(s):  
Experimental Data ◽  
Turbulence Model ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Large Eddy Simulations ◽  
Navier Stokes ◽  
Reynolds Stresses ◽  
Mean Flow ◽  
Navier Stokes Equations ◽  
Large Eddy

The paper reports on the prediction of the turbulent flow field around a three-dimensional, surface mounted, square-sectioned cylinder at Reynolds numbers in the range 104–105. The effects of turbulence are accounted for in two different ways: by performing large-eddy simulations (LES) with a Smagorinsky model for the subgrid-scale motions and by solving the unsteady form of the Reynolds-averaged Navier–Stokes equations (URANS) together with a turbulence model to determine the resulting Reynolds stresses. The turbulence model used is a two-equation, eddy-viscosity closure that incorporates a term designed to account for the interactions between the organized mean-flow periodicity and the random turbulent motions. Comparisons with experimental data show that the two approaches yield results that are generally comparable and in good accord with the experimental data. The main conclusion of this work is that the URANS approach, which is considerably less demanding in terms of computer resources than LES, can reliably be used for the prediction of unsteady separated flows provided that the effects of organized mean-flow unsteadiness on the turbulence are properly accounted for in the turbulence model.

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