Theoretical and Experimental Investigation on Tip Forces and Temperature Distributions of the Brush Seal Coupled Aerodynamic Force

2014 ◽  
Vol 136 (5) ◽  
Author(s):  
Shouqing Huang ◽  
Shuangfu Suo ◽  
Yongjian Li ◽  
Yuming Wang
Keyword(s):  
Aerodynamic Force ◽  
Three Dimensional ◽  
Frictional Coefficient ◽  
Infrared Camera ◽  
Beam Theory ◽  
Aerodynamic Forces ◽  
Balance Principle ◽  
Temperature Distributions ◽  
Brush Seal ◽  
Frictional Coefficients

Based on a type of three-dimensional slice model of a brush seal combined with the commercial CFD software FLUENT, the study calculated the leakage flow of the brush seal. The aerodynamic forces applied on upstream and downstream bristles are analyzed and reduced to a smaller amount of point forces for analysis convenience. The frictional coefficient between the bristle material Haynes 25 and rotor material 1Cr14Mn14Ni are tested. Tip forces including normal reaction and frictional forces caused by aerodynamic forces are quantitatively investigated under conditions with and without frictions using the torque balance principle and nonlinear beam theory (by ANSYS simulations), respectively. Torques, frictional heats, and the temperature distributions of the rotor and bristle pack are studied further. Details and characteristics of the flow and temperature distributions inside the bristle pack are presented. In the experiments, besides traditional tests, such as leakage and torque tests, an infrared camera is employed to capture temperature distributions at the interface of the rotor, bristle pack and nearby zones under various pressure differentials and rotation speeds. The three-dimensional slice model is firstly verified by calculating the leakages, torques and temperature distributions of the brush seal and confirmed via experimentation. The influence of various frictional coefficients and pressure differentials on tip forces, torque and temperature distributions are also examined.

Aerodynamic Forces of Stay Cables Incorporating in Flutier Analysis

2013 ◽  
Vol 438-439 ◽  
pp. 894-900
Author(s):  
Ke Jian Ouyang ◽  
Yi Long ◽  
Bi Cao Peng
Keyword(s):  
Aerodynamic Force ◽  
Three Dimensional ◽  
Wind Tunnel Test ◽  
Test Results ◽  
Stay Cable ◽  
Aerodynamic Forces ◽  
Stay Cables ◽  
Stiffness Matrices ◽  
Flutter Analysis ◽  
Sutong Bridge

With the length of stay cables close to 580m, only inclusion in aerodynamic forces of main deck cannot reflect the actual situation during wind-resistant design. The aerodynamic forces of stay cables should be considered in the three-dimensional flutter analysis of cable-stayed bridges. In this paper, mathematic expressions of unsteady aerodynamic force of stay cable were then derived in terms of aerodynamic damping and stiffness matrices. The above procedure is implemented into NACS by an independent module. As an example, the multimode flutter analysis of Sutong Bridge was conducted by using NACS. Fair agreement is achieved between the present numerical simulation and wind tunnel test results.

scholarly journals Direct Numerical Simulations on the three-dimensional wake transition of flows over NACA0012 airfoil at Re = 1000

2021 ◽  
Vol 13 ◽  
pp. 175682932110556
Author(s):  
Taiba Kouser ◽  
Yongliang Xiong ◽  
Dan Yang ◽  
Sai Peng
Keyword(s):  
Aerodynamic Force ◽  
Angle Of Attack ◽  
Three Dimensional ◽  
Micro Air Vehicles ◽  
Reynold Number ◽  
Angle Of Incidence ◽  
Aerodynamic Forces ◽  
Vortex Pattern ◽  
Naca0012 Airfoil ◽  
Wake Modes

For micro air vehicles (MAV), the precise prediction of aerodynamic force plays an important role. The aerodynamic force of a comparative low Reynold number (Re) vehicle tends to be affected by the different flow modes. In this paper, the aerodynamic performance of a three-dimensional NACA0012 airfoil is studied numerically. A range of angles of attack ( α) 0°−25° and Reynolds number 1000 is considered. Mean and fluctuating coefficients of aerodynamic forces around NACA0012 airfoil are analyzed for different wake modes. The difference of aerodynamic forces between two and three-dimensional simulations are compared. The results show that the wake remains steady two-dimensional for lower angles of attack. At α = 9°, Von Karman vortex pattern is noticed. Flow transition to three-dimensional as the angle of attack increases from α = 13°. 3D wake is found to be stable with parallel shedding mode for 14°-17°. However, these modes become finer with the gradual increase in angle of incidence. While, wake loses its three-dimensional stability to chaotic with gradual increment in angle of attack afterwards.

Aerodynamic Characteristics Analysis of Ultra-High-Speed Elevator with Different Hoistway Structures

2021 ◽  
Author(s):  
Hao Jing ◽  
Qing Zhang ◽  
Ruijun Zhang ◽  
Qin He
Keyword(s):  
High Speed ◽  
Aerodynamic Force ◽  
Three Dimensional ◽  
Aerodynamic Characteristics ◽  
Sudden Increase ◽  
Aerodynamic Forces ◽  
Cross Sectional ◽  
Ultra High Speed ◽  
Characteristics Analysis ◽  
Ventilation Hole

The high-speed airflow generated by ultra-high-speed elevators causes significant aerodynamic force, which seriously reduces the comfort and safety of passengers. First, a multi-parameter general model of ultra-high-speed elevator was established, and the three-dimensional numerical simulation of incompressible flow in the ultra-high-speed elevator was simulated. The correctness of the model and method was verified by experiments and grid-independence analyses. On this basis, the variation in the aerodynamic forces and the pressure in the hoistway was analyzed. Finally, the influence of different hoistway structures and parameters of ventilation holes on the aerodynamic forces and hoistway pressure were analyzed. The results showed that the opening of ventilation holes significantly reduced the aerodynamic forces and hoistway pressure for most of the period of the car’s operation period, but both the aerodynamic forces and hoistway pressure showed a sudden increase–decrease process. The aerodynamic forces and hoistway pressure were highly sensitive to changes in the hoistway blockage ratio, the cross-sectional area of the ventilation hole, and the position of the ventilation hole. When a pair of ventilation holes were opened, those in the middle of the hoistway reduced aerodynamic problems in the hoistway to the greatest extent. The increase in the connection angle between the ventilation hole and the hoistway eliminated the low-speed recirculation zone at the ventilation hole and increased the total volume of exhaust air at the ventilation hole.

scholarly journals Assessing aerodynamic force estimation with experiments and simulations of flapping-airfoil flows on the verge of three-dimensionality

2019 ◽  
Vol 234 (2) ◽  
pp. 428-444 ◽  
Author(s):  
M Moriche ◽  
M Raiola ◽  
S Discetti ◽  
A Ianiro ◽  
O Flores ◽  
...  
Keyword(s):  
Aerodynamic Force ◽  
Numerical Study ◽  
Three Dimensional ◽  
Leading Edge ◽  
Minor Effect ◽  
Two Dimensional ◽  
Force Estimation ◽  
Aerodynamic Forces ◽  
Pitching Airfoil ◽  
Moderate Reynolds Number

This paper reports a combined experimental and numerical study of the flow over a rigid airfoil in flapping motion. The setup consists of a heaving and pitching airfoil at a moderate Reynolds number ([Formula: see text]), at a Strouhal number St = 0.1. The aim is to assess the accuracy of two-dimensional direct numerical simulations in predicting aerodynamic forces in a flow configuration, which is nominally two-dimensional but is at the verge of three-dimensionality. The assessment is carried out with experiments, including flow field and aerodynamic force measurements with particle image velocimetry and a load cell. The comparative study shows a good qualitative agreement between the experiments and the simulations at comparable Reynolds numbers both in terms of forces and flow fields, but with some quantitative differences. The quantitative discrepancies between experiments and simulation are analyzed and reduced to inherent differences between experimental and computational setups. It is observed that the significant differences are apparent almost exclusively in the wake evolution. Nonetheless, this is shown to have a minor effect on the aerodynamic force estimation. Overall, the trends observed when varying the mean pitch angle and the pitching amplitude are the same in both experiments and simulations. This suggests that two-dimensional/three-dimensional effects do not alter significantly the relationship between the unsteady flow mechanisms (i.e. leading edge vortex) and the aerodynamic forces in the parametric range considered here.

scholarly journals State-space aerodynamic model reveals high force control authority and predictability in flapping flight

2021 ◽  
Vol 18 (181) ◽  
pp. 20210222
Author(s):  
Yagiz E. Bayiz ◽  
Bo Cheng
Keyword(s):  
State Space ◽  
Force Control ◽  
Aerodynamic Force ◽  
State Space Model ◽  
Three Dimensional ◽  
Large Degree ◽  
Flapping Wing ◽  
Flapping Flight ◽  
Aerodynamic Forces ◽  
Control Authority

Flying animals resort to fast, large-degree-of-freedom motion of flapping wings, a key feature that distinguishes them from rotary or fixed-winged robotic fliers with limited motion of aerodynamic surfaces. However, flapping-wing aerodynamics are characterized by highly unsteady and three-dimensional flows difficult to model or control, and accurate aerodynamic force predictions often rely on expensive computational or experimental methods. Here, we developed a computationally efficient and data-driven state-space model to dynamically map wing kinematics to aerodynamic forces/moments. This model was trained and tested with a total of 548 different flapping-wing motions and surpassed the accuracy and generality of the existing quasi-steady models. This model used 12 states to capture the unsteady and nonlinear fluid effects pertinent to force generation without explicit information of fluid flows. We also provided a comprehensive assessment of the control authority of key wing kinematic variables and found that instantaneous aerodynamic forces/moments were largely predictable by the wing motion history within a half-stroke cycle. Furthermore, the angle of attack, normal acceleration and pitching motion had the strongest effects on the aerodynamic force/moment generation. Our results show that flapping flight inherently offers high force control authority and predictability, which can be key to developing agile and stable aerial fliers.

A COMPUTATIONAL MODEL FOR ESTIMATING THE MECHANICS OF HORIZONTAL FLAPPING FLIGHT IN BATS

2001 ◽  
Vol 204 (16) ◽  
pp. 2873-2898 ◽  
Author(s):  
PHILIP WATTS ◽  
ERIKA J. MITCHELL ◽  
SHARON M. SWARTZ
Keyword(s):  
Computer Model ◽  
Aerodynamic Force ◽  
Three Dimensional ◽  
Beam Theory ◽  
Metacarpophalangeal Joint ◽  
Flapping Flight ◽  
Internal Reaction ◽  
Order Of Magnitude ◽  
Reaction Forces

SUMMARYWe combine three-dimensional descriptions of the movement patterns of the shoulder, elbow, carpus, third metacarpophalangeal joint and wingtip with a constant-circulation estimation of aerodynamic force to model the wing mechanics of the grey-headed flying fox (Pteropus poliocephalus) in level flight. Once rigorously validated, this computer model can be used to study diverse aspects of flight. In the model, we partitioned the wing into a series of chordwise segments and calculated the magnitude of segmental aerodynamic forces assuming an elliptical, spanwise distribution of circulation at the middle of the downstroke. The lift component of the aerodynamic force is typically an order of magnitude greater than the thrust component. The largest source of drag is induced drag, which is approximately an order of magnitude greater than body form and skin friction drag. Using this model and standard engineering beam theory, we calculate internal reaction forces, moments and stresses at the humeral and radial midshaft during flight. To assess the validity of our model, we compare the model-derived stresses with our previous in vivo empirical measurements of bone strain from P. poliocephalus in free flapping flight. Agreement between bone stresses from the simulation and those calculated from empirical strain measurements is excellent and suggests that the computer model captures a significant portion of the mechanics and aerodynamics of flight in this species.

The Influences of Thermal Effects Induced by the Light-Rub Against the Brush Seal to the Rotordynamics of Turbo Machines

2014 ◽  
Author(s):  
Robert Fay ◽  
Daniel Kreuzer ◽  
Robert Liebich
Keyword(s):  
Temperature Distribution ◽  
Three Dimensional ◽  
Beam Theory ◽  
Contact Forces ◽  
Rotating Speed ◽  
Brush Seal ◽  
Brush Seals ◽  
Institute Of Technology ◽  
Under Construction ◽  
Rotating Coordinates

Brush seals find increasing use in turbomachinery substituting conventional labyrinth seals thanks to their excellent leakage characteristics and convenient integration. Brush seals have very small clearances during operation. In case of contacts between rotor and brush seals, contact forces will be low due to the compliant behaviour of the bristles. While short term contacts between seal and rotor have no significant influence on the rotordynamics, longer-lasting rub can lead to thermally induced rotor-vibrations, also known as the Newkirk-effect. Light partial rub and the subsequently dissipated heat that enters into the shaft may yield a thermal bow performing spiral-vibrations regarding rotating coordinates. Depending on thermal coefficients and rotating speed, this thermal bow may effect instable behaviour with high amplitudes and a possible damage of the machine. At the Chair of Engineering Design and Product Reliability at Berlin Institute of Technology investigations of light partial rub of a rotor against a brush seal are conducted. A test rig is under construction in order to validate the numerically calculated parameters. Investigations are setting up on a thermoelastic model, developed by Kellenberger for a real rotor model. The goals of the investigations are to verify and to extend the model for brush seals and finally to formulate guidelines for the safe use of brush seals in turbomachinery concerning rotordynamics. The difficulty of defining stability statements is to quantify the required thermal parameters. Hence, the three dimensional temperature distribution inside the rotor, which depends on the rotating speed as well, must be known. In order to calculate this temperature distribution the three dimensional Laplace-Equation in cylindrical coordinates is solved for the different convection coefficients by means of Finite-Volume-discretization. Subsequently the required parameters are calculated by numerical integration of the 3-D-structure. The stiffness of the brush seal with respect to a partial rub is calculated using beam theory and continuous elastic support. This paper shows the numerical results of the 3-D temperature distribution, the numerically identified parameters that drive the thermal bow and stability charts regarding spiral vibrations for a chosen brush seal configuration.

scholarly journals The Effect of Inlet Swirl on Brush Seal Bristle Deflections and Stability

2020 ◽  
Vol 142 (7) ◽  
Author(s):  
Yuxin Liu ◽  
John W. Chew ◽  
Michael J. Pekris ◽  
Xiaozhi Kong
Keyword(s):  
Structural Model ◽  
Swirling Flow ◽  
Three Dimensional ◽  
Aerodynamic Forces ◽  
Seal Design ◽  
Dynamic Head ◽  
Brush Seal ◽  
Front Plate ◽  
Static Pressure Difference ◽  
Inlet Swirl

Abstract This paper considers three-dimensional (3D) computational fluid dynamics (CFD) and structural modeling of brush seals, and investigates the effects of inlet swirl on the bristle pack. The model couples aerodynamic forces generated by CFD to a structural model that includes interaction between bristles. At a critical value of inlet swirl, aerodynamic forces cause circumferential slip of the upstream bristle row. In practice, this may lead to instability of the bristle pack and is consistent with anecdotal reports of seal behavior. The critical swirl velocity was reduced when the downstream pressure level was raised, keeping the same upstream total to downstream static pressure difference. This is caused by the increased dynamic head associated with the inlet swirl. Inclusion of a front plate in the seal design does not offer the intended protection to the bristle pack in highly swirling environments. This is associated with highly swirling flow impinging on the bristle tips. Fitting of roughness elements on the upstream face of the front plate could improve stability by reducing swirl of the flow impacting on the bristles. Increasing the bristle diameter and bristle stiffness does not necessarily prevent slip at higher inlet swirl velocities, but reduces the magnitude of slip of the upstream bristles.

Extremely Gusty Winds from a Viewpoint of Aerodynamic Force

2020 ◽  
Author(s):  
Junji Maeda ◽  
Takashi Takeuchi ◽  
Eriko Tomokiyo ◽  
Yukio Tamura
Keyword(s):  
Wind Speed ◽  
Wind Tunnel ◽  
Rise Time ◽  
Aerodynamic Force ◽  
Step Function ◽  
Object Size ◽  
Aerodynamic Forces ◽  
Wind Force ◽  
Wind Observation

To quantitatively investigate a gusty wind from the viewpoint of aerodynamic forces, a wind tunnel that can control the rise time of a step-function-like gust was devised and utilized. When the non-dimensional rise time, which is calculated using the rise time of the gusty wind, the wind speed, and the size of an object, is less than a certain value, the wind force is greater than under the corresponding steady wind. Therefore, this wind force is called the “overshoot wind force” for objects the size of orbital vehicles in an actual wind observation. The finding of the overshoot wind force requires a condition of the wind speed recording specification and depends on the object size and the gusty wind speed.

scholarly journals Analysis of Chemisorbed Tribo-Film for Ceramic-on-Ceramic Hip Joint Prostheses by Raman Spectroscopy

2021 ◽  
Vol 12 (2) ◽  
pp. 29
Author(s):  
Risha Rufaqua ◽  
Martin Vrbka ◽  
Dušan Hemzal ◽  
Dipankar Choudhury ◽  
David Rebenda ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Hyaluronic Acid ◽  
Hip Joint ◽  
Total Joint Replacement ◽  
Film Formation ◽  
Frictional Coefficient ◽  
Synovial Fluids ◽  
Frictional Coefficients ◽  
Joint Prostheses ◽  
Ceramic On Ceramic

To understand the possible lubricant mechanism in ceramic-on-ceramic hip joint prostheses, biochemical reactions of the synovial fluid and the corresponding frictional coefficients were studied. The experiments were performed in a hip joint simulator using the ball-on-cup configuration with balls and cups made from two types of ceramics, BIOLOX®forte and BIOLOX®delta. Different lubricants, namely albumin, γ-globulin, hyaluronic acid and three model synovial fluids, were studied in the experiments and Raman spectroscopy was used to analyze the biochemical responses of these lubricants at the interface. BIOLOX®delta surface was found less reactive to proteins and model fluid lubricants. In contrast, BIOLOX®forte ball surface has shown chemisorption with both proteins, hyaluronic acid and model fluids imitating total joint replacement and osteoarthritic joint. There was no direct correlation between the measured frictional coefficient and the observed chemical reactions. In summary, the study reveals chemistry of lubricant film formation on ceramic hip implant surfaces with various model synovial fluids and their components.

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