Modal Analysis of Receptivity Mechanisms for a Freestream Hot-Spot Perturbation on a Blunt Compression-Cone Boundary Layer

2016 ◽  
Author(s):  
Michael Miselis ◽  
Yuet Huang ◽  
Xiaolin Zhong
Keyword(s):  
Boundary Layer ◽  
Modal Analysis ◽  
Hot Spot

Stability and modal analysis of shock/boundary layer interactions

2016 ◽  
Vol 31 (1) ◽  
pp. 33-50 ◽  
Author(s):  
Joseph W. Nichols ◽  
Johan Larsson ◽  
Matteo Bernardini ◽  
Sergio Pirozzoli
Keyword(s):  
Boundary Layer ◽  
Modal Analysis

Modal Analysis of Cylinder-Induced Transitional Shock-Wave/Boundary-Layer Interaction Unsteadiness

AIAA Journal ◽  
2022 ◽  
pp. 1-19
Author(s):  
Eugene N. A. Hoffman ◽  
Jose M. Rodriguez ◽  
Stephanie M. Cottier ◽  
Christopher S. Combs ◽  
Brett F. Bathel ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Shock Wave ◽  
Modal Analysis ◽  
Layer Interaction ◽  
Wave Boundary Layer ◽  
Boundary Layer Interaction ◽  
Wave Boundary

Fatigue assessment based on hot-spot stresses obtained from the global dynamic analysis and local static sub-model

2019 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Cristiane Oliveira Viana ◽  
Hermes Carvalho ◽  
José Correia ◽  
Pedro Aires Montenegro ◽  
Raphael Pedrosa Heleno ◽  
...  
Keyword(s):  
Dynamic Analysis ◽  
Modal Analysis ◽  
Static Analysis ◽  
Structural Model ◽  
Hot Spot ◽  
Superposition Method ◽  
Hot Spot Stress ◽  
Content Type ◽  
Global Dynamic ◽  
Critical Detail

Purpose The purpose of this paper is to evaluate the fatigue process through the dynamic analysis of the global structural model and local static sub-modelling in a critical detail using the hot-spot stress approach. The detail was studied in three different positions at the “Alcácer do Sal” access viaduct, and the methodologies from the IIW and Eurocode EN 1993-1-9 were compared. Design/methodology/approach In this study, the fatigue life process based on the hot-spot stress approach was evaluated using a global dynamic analysis and a local sub-modelling based on a static analysis of welded connections in the “Alcácer do Sal” railway structure, Portugal, taking into consideration the recommendations from IIW and Eurocode EN 1993-1-9. The hot-spot stresses were calculated through the static analysis of the sub-model of the welded connection for each vibration mode with the aim to obtain the temporal stresses using the modal coordinates and modal stresses of the extrapolation points. The Ansys® and Matlab® softwares were used for the numerical analysis and the hot-spot stress calculations, respectively. Findings The proposed methodology/approach to obtain fatigue assessment is based on the modal analysis of the global structural model and local static sub-modelling. The modal analysis was used to extract the boundary conditions to be used in the local model to determine the temporal stresses of the extrapolation points. Based on the modal superposition method, the stresses as function of time were obtained for fatigue life evaluation of a critical detail by the hot-spot stress approach. The detail was studied in three different positions. Originality/value In the present study, a global-local fatigue methodology based on dynamic analysis of the global structural model and local static sub-modelling of the critical detail using the hot-spot stress approach is proposed. Herein, the modal analysis of the global structural model supported by the modal superposition method was used to obtain the matrix of modal coordinates. The static analysis of the local sub-model for each mode from the modal analysis of global structural model was done to estimate the hot-spot stresses. The fatigue damage calculation was based on S-N curve of the critical detail and rainflow method. The IIW recommendation proved to be more conservative compared to the proposed rules in the Eurocode EN 1993-1-9. The global-local modelling based on dynamic analysis is an important and effective tool for fatigue evaluation in welded joints.

On the Flow and Turbulence Within the Wake and Boundary Layer of a Rotor Blade Located Downstream of an IGV

2003 ◽  
Author(s):  
Yi-Chih Chow ◽  
Oguz Uzol ◽  
Joseph Katz
Keyword(s):  
Boundary Layer ◽  
Spectral Analysis ◽  
Rotor Blade ◽  
Hot Spot ◽  
Wake Flow ◽  
Mean Flow ◽  
Production Rates ◽  
Near Wake ◽  
Trailing Edge ◽  
Planar Shear

This paper presents detailed experimental data on the flow and turbulence within the wake and boundary layer of a rotor blade operating behind a row of Inlet Guide Vanes (IGVs). The experiments are performed in a refractive index matched facility that provides an unobstructed view of the entire flow field. Results of the high-resolution 2D Particle Image Velocimetry (PIV) measurements are used for characterizing the mean flow, Reynolds stresses, turbulent kinetic energy as well as dissipation and production rates. Dissipation and production rates are high and of the same order of magnitude near the trailing edge, and decrease rapidly with increasing distance from the blade. The trend is reversed in the wake kinking region, resulting in elevated turbulence levels, i.e. a turbulent hot spot. One-dimensional spectral analysis shows that, except for the very near wake and hot-spot regions, the turbulence within the rotor wake can be assumed to be isotropic. Also the directions of the maximum shear strain and shear stress are aligned in that region, i.e. consistent with eddy viscosity type Reynolds stress models. The rotor near wake mainly consists of two parallel layers experiencing planar shear with opposite signs as one would expect to find in a 2D wake. However, orientation differences can extend up to 45° near the trailing edge and the hot-spot. Furthermore, there is substantial mismatch in the location of the local maxima of stresses and strains. The values of S33 are also large there, indicating that the flow is three-dimensional. Rotor boundary layer measurements focus on a region where the IGV wake intersects with the rotor blade. The impingement of the increased axial velocity region in between the IGV wakes causes the thinning of the boundary layer. This is similar to the effect of a turbulent jet impinging on a flat surface. When viewed in the frame of reference of “non-wake” flow regions, the boundary layer thinning can also be attributed to the suction (or “negative jet”) effect of the “slip velocity” present in the IGV wake segments. Spectral analysis shows that the turbulence in the rotor boundary layer is highly anisotropic. As a result, the spectra cannot be used for estimating the dissipation rate.

scholarly journals Multi-Wavelength Predictions of the DIM

2004 ◽  
Vol 194 ◽  
pp. 257-257
Author(s):  
M. R. Schreiber ◽  
J.-M. Hameury ◽  
J.-P. Lasota
Keyword(s):  
Boundary Layer ◽  
White Dwarf ◽  
Hot Spot ◽  
Optical Emission ◽  
Local Spectrum ◽  
X Ray ◽  
Multi Wavelength ◽  
On Line ◽  
Extreme Uv ◽  
Reasonable Model

Using the disc instability model (DIM) and a simple but reasonable model for the X-ray, extreme UV, UV and optical emission we investigate the multi-wavelength properties of dwarf novae. We discuss the predictions of the model in the context of the observationally best studied systems, i.e. SS Cyg and VW Hyi. We use the version of the DIM described in Buat-Ménard et al. (2001). The local spectrum of the emission from the disc is assumed to be given by Kurucz (1993,VizieR On-line Data Catalog). We also take into account emission from the (irradiated) secondary, the white dwarf, the hot spot, and the boundary layer.

scholarly journals New methods to cope with temperature elevations in heated segments of flat plates cooled by boundary layer flow

2016 ◽  
Vol 20 (1) ◽  
pp. 45-52 ◽  
Author(s):  
Mohammad Hajmohammadi ◽  
Mohammad Moulod ◽  
Shariatzadeh Joneydi ◽  
Seyed Nourazar
Keyword(s):  
Boundary Layer ◽  
Boundary Layer Flow ◽  
Hot Spots ◽  
Heat Load ◽  
Hot Spot ◽  
Constructal Theory ◽  
Flat Plates ◽  
Convective Boundary ◽  
Layer Flow ◽  
Flow Minimization

This paper documents two reliable methods to cope with the rising temperature in an array of heated segments with a known overall heat load and exposed to forced convective boundary layer flow. Minimization of the hot spots (peak temperatures) in the array of heated segments constitutes the primary goal that sets the platform to develop the methods. The two proposed methods consist of: 1) Designing an array of unequal heaters so that each heater has a different size and generates heat at different rates, and 2) Distancing the unequal heaters from each other using an insulated spacing. Multi-scale design based on constructal theory is applied to estimate the optimal insulated spacing, heaters size and heat generation rates, such that the minimum hot spots temperature is achieved when subject to space constraint and fixed overall heat load. It is demonstrated that the two methods can considerably reduce the hot spot temperatures and consequently, both can be utilized with confidence in industry to achieve optimized heat transfer.

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