Login | Signup now       

Guest

 Click to see how  

HOME | VIDEOS | DOCUMENTS | COLLECTIONS | UPLOAD | BROADCAST | MY ACCOUNT | FEEDBACK | ABOUT

 
Document search results: "turbulent"
 
 Documents
 
   Featured
   Most Viewed
   Most Recent
   Most Discussed
 
 All Subjects
 
  Aeronautics and A...   
  Anthropology   
  Architecture   
  Arts   
  Astronomy   
  Bioengineering   
  Biology   
  Business and Mana...   
  Chemistry and Che...   
  Civil and Environ...   
  Cognitive Science   
  Communications   
  Computer Science   
  Earth and Atmosph...   
  Economics   
  Education   
  Electrical Engine...   
  Energy   
  Entrepreneurship ...   
  History   
  Humanities   
  Journalism   
  Laboratory Equipm...   
  Languages and Lit...   
  Linguistics   
  Material Science ...   
  Mathematics   
  Mechanical Engine...   
  Media Arts   
  Medical Sciences   
  Music   
  Nanoscience and N...   
  Neuroscience   
  Nuclear Engineeri...   
  Oceanography and ...   
  Philosophy   
  Physics   
  Political Science   
  Psychology   
  Public Health   
  Robotics and Arti...   
  Softwares and Pro...   
  Uncategorized   
 

 

 

 

 

 

 

Title          
 Laminar Separation Bubble  
 
Abstract    

This essay focuses on the phenomenon of Laminar Separation Bubble observed at Low Reynolds Numbers. The effect of this bubble on the airfoil characteristics is discussed. Airfoils used at low Reynolds numbers have to be designed taking into consideration the finite space and time occupied by the bubble. Active as well as passive mechanisms to control/delay the formation of the bubble are also mentioned.

For conventional aircraft wings, whose Reynolds number exceeds a million, the flow is typically turbulent with the boundary layer able to strengthen itself by ‘mixing’. Consequently flow doesn’t separate until high angles of attack are encountered. For lower Reynolds numbers, the flow is initially laminar and is prone to separate even under mild adverse pressure gradient. Under certain flow conditions, the separated flow reattaches and forms a Laminar Separation Bubble (Fig. 1) while transitioning from laminar to turbulent state. Laminar separation bubble could modify the effective shape of the airfoil and consequently influence the aerodynamic performance, generally in a negative manner.

The need to understand low Reynolds number (104 to 106) aerodynamics is driven by variety of applicat...

 
Go to document page
 
Added By - anandsaxena
Subject - Aeronautics and Astronautics
Document Type - White Paper
 
   
   

 

Title          
 Modeling and Simulation of Mixing Layer Flows...  
 
Abstract    

Film cooling has been selected for the thermal protection of the composite nozzle extension of the J-2X engine which is currently being developed for the second stage of NASA’s next generation launch vehicle, the Ares I rocket. However,several challenges remain in order to achieve effective film cooling of the nozzle extension and to ensure its safe operation. The extreme complexity of the flow (three-dimensionalwakes, lateral flows, vorticity, and flow separation) makes predicting film cooling performance difficult. There is also a dearth of useful supersonic film cooling data available for engineers to use in engine design and a lack of maturity of CFD tools to quantitatively match supersonic film cooling data. This dissertation advances the state of the art in film cooling by presenting semi-empirical analytical models which improve the basic physical understanding and prediction of the effects of pressure gradients, compressibility and density gradients on film cooling effectiveness. These models are shown to correlate most experimental data well and to resolve several conflicts in the open literature. The core-to-coolant stream velocity ratio, R, and the Kays acceleration parameter, KP, are identified as the critical paramete...

 
Go to document page
 
Added By - kdellimo
Subject - Aeronautics and Astronautics
Document Type - PhD Thesis
 
   
   

 

Title          
 The Role of Density Gradient in Liquid Rocket...  
 
Abstract    

Experimental and analytical studies were conducted to investigate key physical mechanisms responsible for flame-acoustic coupling during the onset of acoustically driven combustion instabilities in liquid rocket engines (LREs). Controlled experiments were conducted in which a turbulent hydrogen-oxygen (GH2-GO2) diffusion flame, established downstream of a two-dimensional model shear coaxial injector was acoustically forced by a compression driver unit mounted in a transverse direction and excited through a broad range of frequencies (200Hz-2000Hz) and amplitudes. Characteristic interactions between flame and acoustics visualized through OH* and CH* chemiluminescence imaging and dynamic pressure measurements obtained using high frequency dynamic pressure transducers indicated that small acoustic disturbances could be amplified by flame-acoustic coupling under certain conditions leading to substantial modulation in spatial heat release fluctuations. Density gradient between fuel and oxidizer was found to significantly affect the way acoustic waves interacted with density stratified flame fronts. The particular case of an asymmetric flame front oscillation under transverse acoustic forcing indicated that baroclinic vorticity, generat...

 
Go to document page
 
Added By - A Ghosh
Subject - Aeronautics and Astronautics
Document Type - PhD Thesis
 
   
   

Page 1 of 1