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so

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the nasa lewis research center is in a

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unique position

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to take advantage of computational fluid

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dynamics

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structural mechanics and material

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science

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to develop new techniques for

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multi-component

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multi-discipline analysis design

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and optimization of advanced engine

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systems

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to that end many of the lewis

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organizations have formed research teams

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whose activities are directed towards a

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common long-range vision

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of a numerical test cell for studies on

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advanced

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engine systems this unique computational

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capability

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in turn sets the stage for new levels of

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understanding once the scientist or

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engineer is satisfied

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that the critical physics are being

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modeled in the analysis

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however confidence in computational

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science

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can only be achieved by detailed

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comparison

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with experimental data obtained in test

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cells

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or wind tunnels one such validation

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experiment was performed in the 10 by 10

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foot

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supersonic wind tunnel at the nasa lewis

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research center

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in cleveland ohio in this experiment

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instrumentation was installed in a

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supersonic inlet

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designed for mach 5 to provide detailed

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data

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for code validation a 3d

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viscous computer simulation of this

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inlet

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revealed previously unknown strong

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secondary flows

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as can be seen from these particle

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traces

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these secondary flows are formed because

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of shock wave

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interactions with the turbulent side

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wall boundary layers

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and they create additional inlet losses

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the close coupling between analysis and

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the validation experiment

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was designed to confirm both the cause

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and effect

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of these previously unknown secondary

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flows

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a second important application of

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computational fluid dynamics

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is to analyze new concepts in propulsion

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such as this supersonic fan blade

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designed using a 2d

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analysis a 3d viscous computer

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simulation

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predicted blade pressures shown here in

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varying colors

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the simulation also allowed designers

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and engineers to visualize secondary

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flow

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here particle traces show the passage

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vortex

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which can be traced to its origin as a

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horseshoe vortex

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ahead of the blade a third application

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of computational fluid dynamics at nasa

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lewis research center

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lies in the study of interactions which

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are difficult to measure

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such as this supersonic combustor

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the combustion process shown was modeled

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as two hydrogen jets

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operating at a pressure ratio of eight

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and injecting into a rectangular duct

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compression waves are generated upstream

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of each

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jet as can be seen from these color

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contours

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on the top wall the two jets create an

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adverse pressure gradient which causes

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the free stream particles to move

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outward laterally

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as well as downward the jets are bent

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by the free stream the second jet

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penetrates more deeply

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into the free stream flow than the first

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jet

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mixing of hydrogen

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and air and consequently more complete

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combustion computational fluid dynamics

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is also being used

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to study the interaction of the external

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environment

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with a propulsion system in this example

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an under expanded 3d asymmetric nozzle

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at a pressure ratio of 10 exhaust

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supersonically into quiescent air

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nozzle flow expands laterally downstream

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of the lower lip compression waves

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reflect

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off the upper and lower shear layers and

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a very thin

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the high temperature high stress

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requirements of modern aircraft engines

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necessitate the development of novel

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materials

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the study of which can greatly benefit

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from computational material science

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metals ceramics polymers and composites

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of these

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are all employed to satisfy the high

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temperature

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strength and durability requirements

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material science is concerned with

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phenomena that range from rapid material

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processes

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with solidification rates measured in

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meters per second

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in melt spinning to deposition rates of

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microns per hour

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in chemical vapor deposition

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temperature coatings

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fibers and semiconductors such as

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silicon carbide are

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made this process involves injecting a

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nutrient gas

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into a reactor in which the gas then

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undergoes several

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gas phase chemical reactions as it

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passes across

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a heated susceptor subsequent surface

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reactions deposit the needed materials

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in this case silicon on the susceptor

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the computer simulation shown includes

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the 3d aspects of the reactor

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strong natural buoyancy causes

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substantial distortions of convecting

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fields

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shown here as path lines of neutrally

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buoyant particles

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subsequent distortions in both the

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temperature and reacting species fields

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are evident resulting in severe

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non-uniformities

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in coating thickness and structure

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additional analyses show an excellent

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agreement between the experimental and

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numerical deposition rates on the

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susceptor

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this study shows that computational

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material science

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can provide information important for

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the understanding

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and design of new materials

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the nasa lewis research center couples

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computational and experimental programs

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for efficiently meeting the requirements

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of modern aircraft engines

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the development and practical

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application of advanced numerical

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simulation codes

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for propulsion systems will require

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increases

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in computing power that is speed

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and memory these advances will have to

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be matched by improvements in

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computational support

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program development and computer

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graphics

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important because of the massive amounts

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of data that need to be understood

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the lewis goal in scientific computing

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is to provide high performance graphics

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workstations

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having access to parallel processors

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mainframe

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and supercomputers nasa lewis research

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center is moving as rapidly as possible

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towards the establishment of a

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high-performance computing environment

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that will satisfy the long-term

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experimental