Ragnar Larusson

Doktorand at Department of Applied Mechanics, Fluid Dynamics

Since January 2012, Ragnar has been immersed in the compressible and supersonic world of internal flows in rocket engine nozzles. His work is focused on the infamous side-load problem. Here is a sneak preview from his upcoming paper that describes, in short, this side-load problem; "Modern space vehicles take off using a combination of solid rocket boosters and rocket engines. During the startup of a rocket engine at sea level the flow separates from the nozzle wall because of the over expansion of the nozzle. This creates an attached shock inside the nozzle and due to the sudden pressure rise across the attached shock, any asymmetry of the shock location along the circumference of the nozzle can cause side loads, potentially harmful to the nozzle structure and the engine"This phenomenon described above has been extensively researched over the past decades. The current research project that Ragnar is involved in aims to add to the existing and limited understanding of the phenomenon by means of advanced numerical simulation methods. The Swedish National Space Board is greatly acknowledged for funding the project, as is GKN Aerospace Engine Systems in Trollhättan for technical guidance. Supervising the project are Niklas Andersson and Lars-Erik Eriksson at Chalmers and Jan Östlund at GKN.Ragnar's Academic BackgroundRagnar holds a B.Sc. Degree in mechanical engineering from the University of Iceland. He earned his M.Sc. Degree in solid and fluid mechanics from Chalmers in 2011. During his masters thesis work and after graduation he had a brief encounter with external flow simulations around bluff bodies such as a rudimentary airplane landing gear and pyramids. In that work he used the Large Eddy Simulation method and the new and exciting Partially Averaged Navier-Stokes method.

Source: chalmers.se

Projects

2012–2014

Modal Decomposition of Separated Nozzle Flow

Lars-Erik Eriksson Department of Applied Mechanics, Fluid Dynamics
Niklas Andersson Department of Applied Mechanics, Fluid Dynamics
Ragnar Larusson Department of Applied Mechanics, Fluid Dynamics
Swedish National Space Board

There might be more projects where Ragnar Larusson participates, but you have to be logged in as a Chalmers employee to see them.

Publications

2017

Modal Analysis of Supersonic Flow Separation in Nozzles

Ragnar Lárusson,
Doctoral thesis
2017

Dynamic Mode Decomposition Applied to a Detached-Eddy Simulation of Separated Nozzle Flow

Ragnar Lárusson, Markus Burak, Niklas Andersson et al
Proc. of the 55th AIAA Aerospace Sciences Meeting, AIAA SciTech Forum
Conference paper - non peer reviewed
2016

Hybrid RANS-LES Simulation of Separated Nozzle Flow

Ragnar Lárusson, Niklas Andersson, Jan Östlund et al
Proc. of the 52nd AIAA/SAE/ASEE Joint Propulsion Conference Salt Lake City, UT
Conference paper - non peer reviewed
2014

Investigation of Screech in Supersonic Jets Using Modal Decomposition

Ragnar Lárusson, Haukur Hafsteinsson, Niklas Andersson et al
Proceedings of NSCM-27: the 27th Nordic Seminar on Computational Mechanics, p. 25-28
Conference paper - non peer reviewed
2014

Comparison of Eigenmode Extraction Techniques for Separated Nozzle Flows

Ragnar Lárusson, Niklas Andersson, Lars-Erik Eriksson et al
50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and exhibit 2014; Cleveland; United States; 28 July 2014 through 30 July 2014
Conference paper - peer reviewed
2014

Investigation of supersonic jet flow using modal decomposition

Ragnar Lárusson, Haukur Hafsteinsson, Niklas Andersson et al
20th AIAA/CEAS Aeroacoustics Conference
Conference paper - peer reviewed
2014

Investigation of a Separated Nozzle Flow with Transonic Resonance Using Dynamic Mode Decomposition

Ragnar Lárusson, Niklas Andersson, Lars-Erik Eriksson et al
Report
2014

Modal Decomposition of Separated Nozzle Flow

Ragnar Lárusson,
Licentiate thesis
2013

Linear Stability Analysis Using the Arnoldi Eigenmode Extraction Technique Applied to Separated Nozzle Flow

Ragnar Lárusson, Niklas Andersson, Lars-Erik Eriksson et al
49TH AIAA/ASME/SAE/ASEE JOINT PROPULSION CONFERENCE, July 14 - 17, 2013. San Jose, CA, USA
Conference paper - peer reviewed
2012

Large eddy simulations of the flow around pyramids

Sinisa Krajnovic, Ragnar Lárusson,
Proceedings CFD society of canada conference, May 2012, Canmore, Canada
Conference paper - peer reviewed
2012

Superiority of PANS compared to LES in predicting a rudimentary landing gear flow with affordable meshes

Sinisa Krajnovic, Ragnar Lárusson, B. Basara et al
International Journal of Heat and Fluid Flow. Vol. 37, p. 109-122
Scientific journal article - peer reviewed
2011

PANS of Rudimentary Landing Gear

Sinisa Krajnovic, Ragnar Lárusson, Eysteinn Helgason et al
6th AIAA Theoretical Fluid Mechanics Conference, Honolulu, 27 - 30 June 2011 (AIAA paper 2011-3109)
Conference paper - peer reviewed