Dynamic Response of Biomimetic Hair Receptors in Both Steady and Unsteady Flow Environment

2013 ◽  
Author(s):  
Manohar Chidurala ◽  
Benjamin T. Dickinson ◽  
Uttam K. Chakravarty
Keyword(s):  
Dynamic Response ◽  
High Performance ◽  
Stokes Equations ◽  
Beam Theory ◽  
Element Model ◽  
Creeping Flow ◽  
Mode Shapes ◽  
Flow Environment ◽  
Oscillatory Component ◽  
Hair Sensors

The high performance of nature’s creations and biological assemblies has inspired the development of engineered counter parts that may outperform or provide new capabilities to conventional systems. In particular, the wings of bats contain distributed arrays of micro-scaled flow sensitive hair receptors over their surface, which inspires artificial hair sensors (AHS) development in aerodynamic feedback control designs using the micro-electro-mechanical systems (MEMS). One approach investigates the possibility of installing AHS on the leading edges of the wings of small-scaled unmanned aerial vehicles (UAVs) to improve the aerodynamic control. Our major motivation for the present study is that current mathematical models have limited relevance to aerodynamic situations because they are analyzed in steady or purely oscillatory flows. Our overall objective is to understand AHS fluid-structure interaction (FSI) in flow regimes relevant to small-scaled UAVs, for which we speculate a steady baseline flow perturbed by an oscillatory component is an appropriate flow reference condition. Towards understanding the AHS in this situation, we investigate the dynamic response of a hair receptor in a creeping flow environment with a steady and oscillatory component. We present time varying deflection and bending moment of the artificial hair sensors at different freestream velocities. For this, a three-dimensional FSI model is developed for the flexible hair-structure in the airflow, which is coupled with a finite element model using the computational fluid dynamics (CFD). The Navier-Stokes equations including continuity equation are solved numerically for the CFD model. To describe the dynamic response of the hair receptors, the natural frequencies and mode shapes of the hair receptors, computed from the FSI model, are compared with the excitation frequencies of the surrounding airflow. This model also describes both the boundary layer effects and effects of inertial forces due to FSI of the hair receptors. For supporting the FSI model, the dynamic response of the hair receptor is also validated considering the Euler-Bernoulli beam theory including the steady and unsteady airflow.

Comparison of frequency- and time-domain analyses for guyed masts in turbulent winds

2006 ◽  
Vol 33 (2) ◽  
pp. 169-182 ◽  
Author(s):  
B F Sparling ◽  
L D Wegner
Keyword(s):  
Finite Element ◽  
Dynamic Response ◽  
Dynamic Analysis ◽  
Frequency Domain ◽  
Time Domain ◽  
Element Model ◽  
Mode Shapes ◽  
Nonlinear Behaviour ◽  
Element Analysis ◽  
Guyed Mast

Both frequency- and time-domain methods have been employed in the dynamic analysis of guyed telecommunication masts subjected to turbulent winds. Although the probabilistic frequency-domain approach offers some advantages in terms of its relative ease of implementation and in the statistical reliability of wind load descriptions, the deterministic time-domain method permits a more realistic treatment of system nonlinearities. In this study, a numerical investigation was undertaken to compare frequency- and time-domain dynamic response predictions for a selected guyed mast in gusty winds. Two different analysis techniques were employed, with the frequency-domain calculations performed using response influence lines and the time-domain analyses carried out using a stiffness-based finite element model. Good agreement was observed in root-mean-square and peak dynamic response estimates after compensation was included for differences in turbulence intensity levels assumed in the two models. In general, natural frequencies and mode shapes were also similar.Key words: guyed mast, dynamic analysis, wind, turbulence, nonlinear behaviour, finite element analysis, cables, frequency domain, time domain.

Finite Element Modelling of a Generic Rotor-Bearing System and Experimental Validation

2015 ◽  
Author(s):  
A. Rehman ◽  
K. S. Ahmed ◽  
F. A. Umrani ◽  
B. Munir ◽  
A. Mehboob ◽  
...  
Keyword(s):  
Finite Element ◽  
Dynamic Response ◽  
Finite Element Model ◽  
Element Model ◽  
Mode Shapes ◽  
Efficient Operation ◽  
Critical Speeds ◽  
Rotor Bearing ◽  
The Impact ◽  
Bearing System

The design and development of the rotating machinery require a precise identification of its dynamic response for efficient operation and failure prevention. Determination of critical speeds and mode shapes is crucial in this regard. In this paper, a finite element model (FEM) based on the Euler beam theory is developed for investigating the dynamic behavior of flexible rotors. In-house code in Scilab environment, an open source platform, is developed to solve the matrix equation of motion of the rotor-bearing system. The finite element model is validated by the impact hammer test and the dynamic testing performed on the rotors supported on a purpose-built experimental setup. Bearing stiffness is approximated by using the Hertzian contact theory. Obtaining the critical speeds and mode shapes further improves the understanding of dynamic response of rotors. This study paves way towards advanced research in rotordynamics in Faculty of Mechanical Engineering, GIK Institute.

Experimental and Numerical Analysis of Read/Write Head Suspension Dynamics for High-Performance Floppy Drive Systems

1990 ◽  
Vol 112 (1) ◽  
pp. 26-32 ◽  
Author(s):  
G. M. Frees ◽  
D. K. Miu
Keyword(s):  
Finite Element ◽  
Numerical Analysis ◽  
High Performance ◽  
Laser Doppler Vibrometer ◽  
Numerical Data ◽  
Floppy Disk ◽  
Element Model ◽  
Operating Conditions ◽  
Tracking Performance ◽  
Mode Shapes

Read/write head suspensions are critical components of high-performance floppy disk drives. Their dynamics affect head/media compliance, wear, and tracking performance. Vibration measurements are necessary in order to verify and adjust finite element models, to observe the influence of actual loading and operating conditions, and to study the effects of unmodeled components such as electrical wires and adhesives. A nonintrusive measurement technique using a Laser Doppler Vibrometer is utilized to measure the submicron vibrations. Excitation of the suspension is provided by a specially designed miniature air hammer and a piezoelectric transducer. Natural frequencies and mode shapes are extracted from the measurements and compared with numerical data from the finite element model. Research shows that boundary conditions are the most important parameters in the modeling of the suspension. A new design is proposed, using the verified model, to increase the tracking performance of the suspension. Synergy between experimentation and numerical analysis is emphasized.

A FEniCS-based model for prediction of boundary layer transition in low-speed aerodynamic flows

2019 ◽  
Vol 233 (15) ◽  
pp. 5729-5745
Author(s):  
Amir Kolaei ◽  
Götz Bramesfeld
Keyword(s):  
Boundary Layer ◽  
High Performance ◽  
Stokes Equations ◽  
Element Model ◽  
Least Square ◽  
Boundary Layer Transition ◽  
Navier Stokes ◽  
Layer Transition ◽  
Low Speed ◽  
Aerodynamic Flows

In the paper, a finite element model is developed that predicts boundary layer transition in low-speed aerodynamic flows. The model is based on a Reynolds-averaged Navier-Stokes approach, where the incompressible form of the Navier-Stokes equations is solved together with a three-equation eddy-viscosity model utilizing the FEniCS framework. A least-square stabilized Galerkin method is employed in order to prevent numerical oscillations that can arise from dominant advection terms. The proposed FEniCS model is ideal for applications with complex geometries and is tested on high performance computing platforms for parallel processing. The FEniCS model is validated by comparing the skin friction coefficient as well as profiles of velocity and total fluctuation kinetic energy with the benchmark experimental data for transitional boundary layers on a flat plate. The validity of the solver is further examined using experimental measurements reported for a NLF(1)-0416 natural laminar flow airfoil at different angles of attack. The airfoil results are also compared with those obtained using XFOIL, a well-known tool for the design of two-dimensional airfoils. These comparisons suggest that the proposed FEniCS-based model can effectively simulate aerodynamic flow fields that involve laminar-to-turbulent transition.

Dynamic response of a historical armory building using the finite element model validated by the ambient vibration test

2018 ◽  
Vol 24 (22) ◽  
pp. 5472-5484 ◽  
Author(s):  
Ahmet Can Altunişik ◽  
Ali Fuat Genç ◽  
Murat Günaydin ◽  
Fatih Yesevi Okur ◽  
Olguhan Şevket Karahasan
Keyword(s):  
Finite Element ◽  
Dynamic Response ◽  
Finite Element Model ◽  
Dynamic Characteristics ◽  
Nonlinear Dynamic ◽  
Element Model ◽  
Ambient Vibration ◽  
Nonlinear Material ◽  
Mode Shapes ◽  
Nonlinear Dynamic Response

In this paper, the aim was to determine the nonlinear dynamic response of historical masonry armory buildings using a validated finite element model. Eight ambient vibration tests were conducted on the building, using three different measurement test setups to extract the dynamic characteristics using the Enhanced Frequency Domain Decomposition method. A finite element model was constructed in ANSYS and the dynamic characteristics were obtained numerically. It can be seen that there is a good correlation between the mode shapes, but there are differences in natural frequencies with maximum values of 10.1%, 7.4% and 13.4% for first the three modes. To determine the nonlinear dynamic response, the validated finite element model was analyzed using the Kocaeli earthquake motion. The Drucker–Prager criterion and Willam–Warnke surface were considered for the nonlinear material models. At the end of the analyses, maximum displacements, principal stresses and strains are given in detail using contour diagrams. It is evident that the displacements show an increasing trend from the base to the top point of the building. Stresses occurred on the corners, openings and transition segments. In addition, crack distribution diagrams were drawn up to illustrate the stress accumulation points.

Three-Dimensional Dynamic Analysis of Sluice Structure

2012 ◽  
Vol 490-495 ◽  
pp. 845-849
Author(s):  
Xiao Yan Zhang ◽  
Ze Li ◽  
Long Wang
Keyword(s):  
Finite Element ◽  
Dynamic Response ◽  
Natural Vibration ◽  
Response Spectrum ◽  
Three Dimensional ◽  
Element Model ◽  
Mode Shapes ◽  
Stress Concentrations ◽  
The Finite Element Model ◽  
Dynamic Stress Concentrations

In this paper a sluice project is taken as an example. Dynamic finite element method is used to analyze dynamic response of sluice structure under the action of seismic acceleration (0.157g). The subspace iterative method is used in the modal analysis of the sluice structure after the finite element model is established, the natural vibration frequencies, and mode shapes are obtained. And then the response spectrum method is employed to implement dynamic response of the structures. The results show that the dynamic stress concentrations take place on some regions

scholarly journals Revisiting Surface-Subsurface Exchange at Intertidal Zone with a Coupled 2D Hydrodynamic and 3D Variably-Saturated Groundwater Model

Water ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 902
Author(s):  
Zhi Li ◽  
Ben R. Hodges
Keyword(s):  
Intertidal Zone ◽  
Coastal Wetlands ◽  
High Performance ◽  
Stokes Equations ◽  
Wave Model ◽  
Surface Flow ◽  
Richards Equation ◽  
Navier Stokes ◽  
Dynamic Surface ◽  
Flow Equations

A new high-performance numerical model (Frehg) is developed to simulate water flow in shallow coastal wetlands. Frehg solves the 2D depth-integrated, hydrostatic, Navier–Stokes equations (i.e., shallow-water equations) in the surface domain and the 3D variably-saturated Richards equation in the subsurface domain. The two domains are asynchronously coupled to model surface-subsurface exchange. The Frehg model is applied to evaluate model sensitivity to a variety of simplifications that are commonly adopted for shallow wetland models, especially the use of the diffusive wave approximation in place of the traditional Saint-Venant equations for surface flow. The results suggest that a dynamic model for momentum is preferred over diffusive wave model for shallow coastal wetlands and marshes because the latter fails to capture flow unsteadiness. Under the combined effects of evaporation and wetting/drying, using diffusive wave model leads to discrepancies in modeled surface-subsurface exchange flux in the intertidal zone where strong exchange processes occur. It indicates shallow wetland models should be built with (i) dynamic surface flow equations that capture the timing of inundation, (ii) complex topographic features that render accurate spatial extent of inundation, and (iii) variably-saturated subsurface flow solver that is capable of modeling moisture change in the subsurface due to evaporation and infiltration.

Analysis of Material Coating for Damping in Beam Structures

2010 ◽  
Vol 442 ◽  
pp. 202-210
Author(s):  
S.H. Raza ◽  
M.A. Malik ◽  
W. Akram
Keyword(s):  
Turbine Blades ◽  
Beam Theory ◽  
Industrial Applications ◽  
Theory Model ◽  
Design Tool ◽  
Coating Material ◽  
Mode Shapes ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Finite Element Procedure

Vibratory stresses are the main cause of material failure in aerospace/mechanical structures and machine components. Failure also occurs due to these vibratory stresses in gas turbine engines and rotating machinery components while operating at resonant frequency. A magnetomechanical coating material is used as a very effective method for damping of these stresses. Vibratory stress damping in components like turbine blades through magnetomechanical coating material is well known in literature. However, the geometric correlations for the varying coated beam are not well established. We have utilized a cantilever beam as the basic geometry for this investigation to establish a correlation for varying coating. Beam theory is applied as a mathematical model for obtaining the mode shapes for the beam. A finite element procedure is performed to acquire the data and this data is then correlated with beam theory model for initial verification. This data is further evaluated to form the required model for calculating thickness of coating for a beam. The resulting parametric correlation is verified through comparison with the already published experimental data available in literature. This correlation can be used as a design tool for suppression of vibratory stresses in industrial applications.

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