What are the key concepts in numerical simulations of Ram Accelerator devices?

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Discussion Overview

The discussion revolves around the numerical simulations of Ram Accelerator devices, including comparisons with Ramjet and Scramjet engines. Participants explore various aspects of these devices, including their operational modes, design differences, and the specifics of their simulations.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant seeks resources for learning about Ram Accelerator devices and expresses confusion about the differences between Scramjet and Ramjet engines.
  • Another participant explains that Scramjets are designed for supersonic combustion, while Ramjets typically involve subsonic combustion due to shockwaves in their combustion chambers.
  • A later reply introduces the concept that Ramjets can operate in multiple modes: subdetonative, transdetonative, and superdetonative, with the last being associated with Scramjets.
  • Participants discuss their final projects related to Ram Accelerators, focusing on simulating acceleration as a function of Mach number and the initial state of propellant and projectile geometry.
  • There is a debate about the dimensionality of flow in Ram Accelerators, with one participant asserting that the flow is two-dimensional, while another mentions using a one-dimensional model for thrust calculations.
  • Participants mention using specific computational tools and models, such as the Euler Reactive Equations and Chemkin package, for their simulations.

Areas of Agreement / Disagreement

Participants express differing views on the operational characteristics of Ramjets and Ram Accelerators, particularly regarding combustion modes and flow dimensionality. The discussion remains unresolved with multiple competing perspectives on these topics.

Contextual Notes

Participants reference various operational modes of Ramjets and the complexities of simulating flow dynamics, indicating potential limitations in their understanding or the models they are using.

Who May Find This Useful

Students and researchers interested in propulsion systems, numerical simulations, and the technical aspects of Ram Accelerator and related engine technologies.

Clausius2
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I've just got my final year project assigned. It has to do with a numerical simulation of a Ram Accelerator device.

Well, apart of having doubts, which I will post just here proximately, I would want to know some website to learn more about that type of device.

Apart of Google sites, which is my task to find them, do you know some website dedicated to that or some academic site for further explanation?.

Thanks in advance.

EDIT: Notwithstanding how much I've been googling, I haven't found the difference between Scramjet and Ramjet engine. Anybody knows it?
 
Last edited:
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Clausius2 said:
EDIT: Notwithstanding how much I've been googling, I haven't found the difference between Scramjet and Ramjet engine. Anybody knows it?
Not much - the difference is that the scramjet is shaped to optomize flow for supersonic combustion (that's what the "sc" stands for).
 
russ_watters said:
Not much - the difference is that the scramjet is shaped to optomize flow for supersonic combustion (that's what the "sc" stands for).

Thanks.

Doesn't have also the Ramjet a supersonic combustion in his combustion chamber?. Furthermore what's the design's difference between a Ramjet engine and a Ram Accelerator?. I'll keep on surveying over there...
 
Well I only googled and came up with the links below. Hope it helps.

Ram accelerator

http://www.nas.nasa.gov/About/Education/SpaceSettlement/Nowicki/SPBI106.HTM

http://www.aa.washington.edu/AERP/ramac/uw_facility.html

Scramjet

http://elroy.anu.edu.au/~frank/houwing/papers/journal/SeanChokingPaper.pdf

http://www.wordiq.com/definition/Scramjet#Theory

http://www.aviation-history.com/engines/ramjet.htm

http://www.physics.uq.edu.au/lp/lasdiag/scram.html

http://www.pr.afrl.af.mil/mar/2002/feb2002.pdf

http://www.tc.cornell.edu/Research/CMI/RLVsource/scramjets.html
 
Last edited by a moderator:
Thanks for your effort, Geniere, very helpful.
 
Clausius2 said:
Doesn't have also the Ramjet a supersonic combustion in his combustion chamber?.

I don't think so. Normal shockwave out front of the combustion chamber slows the flow to subsonic speeds.
 
enigma said:
I don't think so. Normal shockwave out front of the combustion chamber slows the flow to subsonic speeds.

I have received your e-mail. And I have answered you to your gmail direction. Thank you very much.

Well, after being reading the RAM articles at University of Washington web, the ramjet engine can operate under supersonic combustion. In fact, there are three modes of operating of the ramjet engine:

-Subdetonative: the combustion is produced subsonically as you have just said.

-Transdetonative: there is transonic flow in the combustion chamber.

-Superdetonative: the combustion is made supersonically. Furthermore, this last mode is the so-called ScRamjet. Also, the RAM accelerator can operate in those three modes, the superdetonative is called ScRam accelerator.

This thread is not closed at all. You could comment all what you want about this subject. Proximately I will post some new doubts.
 
What a coincidence;)! My final project is also about a ramac! At the moment I was searching for something related to the chemical kinetic process.. and I came across your post! What exactly do you want to simulate (inputs-outputs)?
 
julesverne said:
What exactly do you want to simulate (inputs-outputs)?

What do you mean with that?

PD: I don't believe in coincidences, :P
 
  • #10
Sorry if I didn't explain myself very well..Basically, what I have to do is to calculate the generated acceleration as a function of Mach number given the initial state of the in-tube propellant and projectile geometry... using a relative simple one-dimensional unsteady flowfield model. Is that what you have to do as well?
 
  • #11
julesverne said:
Sorry if I didn't explain myself very well..Basically, what I have to do is to calculate the generated acceleration as a function of Mach number given the initial state of the in-tube propellant and projectile geometry... using a relative simple one-dimensional unsteady flowfield model. Is that what you have to do as well?

Hi Jules Verne (I never believed me talking with such a important writter :biggrin: ). What do you mean with a relative simple one-dimensional unsteady flow field. The flow over a RAMAC is two dimensional.

Anyway, my target is to code the Euler Reactive Equations and obtain the three modes of functioning. Designing the projectile and geometry is left to me. A simple kinetic mechanism of Hydrogen will be surely implemented. But I have not chewed over it yet.
 
  • #12
Clausius2 said:
What do you mean with a relative simple one-dimensional unsteady flow field. The flow over a RAMAC is two dimensional.

Anyway, my target is to code the Euler Reactive Equations and obtain the three modes of functioning. Designing the projectile and geometry is left to me. A simple kinetic mechanism of Hydrogen will be surely implemented. But I have not chewed over it yet.

Good luck! I just have to study the subdetonative mode ;).. The 1-D modeling I'm using is for calculating the thrust (the classical thermodynamic "black box" model). The problem is that the control volume length depends on mach number, so I'm trying to figure out the induction length as a function of mach number, which would give an idea of the c.v.length variation.By the moment, I'm trying to get used to chemkin package which, according to my teachers, will help me a lot with the kinetic calculations :rolleyes: The shock wave system is obviusly 2-D, but I'm not looking at it at the moment. I will use methane as fuel.
 

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