Ehsan Roohi Golkhatmi

External Links

The views expressed on faculty and external web pages are those of the author and do not necessarily represent those of Embry-Riddle Aeronautical University.

Biography

Ehsan Roohi, born in Mashhad, Iran, in July 1982, holds the position of Visiting Associate Professor at Embry-Riddle Aeronautical University. He earned his Ph.D. in aerospace engineering from Sharif University of Technology, a leading Iranian engineering institution, in 2010, with a sabbatical visit to the University of Strathclyde, UK. Previously, he served as a University Professor at Ferdowsi University of Mashhad and Xi’an Jiaotong University, and worked as a researcher at University of Maryland and a lecturer at Johns Hopkins University. 
Roohi specializes in direct simulation Monte Carlo (DSMC) techniques and has contributed extensively to the field through his research on new collision models in DSMC, and new micro-scales pumps working with heat dissipations. His work has been published in esteemed journals such as Physics Reports, Journal of Computational Physics, Physics of Fluids, and Journal of Fluid Mechanics. His publication record includes 130 papers indexed in Scopus, with an H-index of 37 (Scopus), 36 (WoS), and 41 (Google Scholar), and an I-10 index of 97 (Google Scholar). His research has garnered over 3803 citations in Scopus.
Additionally, Roohi is actively engaged in the scholarly community, having conducted more than 550 certified reviewer activities for papers indexed in the Web of Science. He serves as an associate editor for two journals: Journal of Fluid Engineering (ASME) and International Journal of Modern Physics C (World Scientific). He has also served as a guest editor for special issues in prestigious journals such as Fluids and Physics of Fluids.
Roohi's research endeavors have received support from renowned institutions, including the Iran National Science Foundation and China Ministry of Science and Technology. Demonstrating his commitment to nurturing future researchers, Roohi has supervised over 40 MSc students in Iran and China, as well as 5 PhD students.
In addition to his research contributions, Roohi has extensive teaching experience since 2010, delivering courses in fluid dynamics, gas dynamics, and renewable energies at both undergraduate and graduate levels in Iran, China and USA. He also published three textbooks on Gas Dynamics, Rarefied Gas Dynamics and Fluid Mechanics at Micro and Nano Scales.

Education

• Ph.D. - Doctor of Philosophy in Aerospace Engineering: Propulsion, Sharif University of Technology

Currently Teaching

• AE 319: Aerodynamics
• AE 414: Space Propulsion

Courses Taught

Fluid Dynamics II, Johns Hopkins University

Publications

Research

Ehsan Roohi mainly works on novel and intelligent collision models in the direct simulation Monte Carlo (DSMC) technique framework to make the rarefied flow simulations more accurate and less time-consuming [3]. The collision process is the most sophisticated part of DSMC, which is treated probabilistically [4]. He has demonstrated the shortcomings of conventional collision models [5] and has been developing innovative intermolecular collision paradigms in the framework of the DSMC. In 2015, he improved the “Simplified Bernoulli” trial (SBT) collision model [6] by introducing an intelligent version, [7] and he was the lead developer of a new collision model called the “Generalized Bernoulli” trial (GBT) scheme in 2018 [8].

In 2022, he developed another model, the “Symmetrized and Simplified Bernoulli” trial (SSBT) scheme, [9] that has improved performance compared to previous ones. In the same year, Stefan Stefanov and he suggested a hybrid collision scheme on transient adaptive subcells to treat various types of rarefied gas flows at the hypersonic regime [10]. He has been developing numerical tools to perform simulations of hypersonic space re-entry vehicles, waveriders, and propulsion of arrays of small-scale satellites much faster with high reliability [11]. During his research career, he contributed to developing the very first open-source DSMC code in the framework of OpenFOAM, i.e., dsmcFoam [12]. His next plan is to incorporate physics-informed machine learning and deep learning methods into ab-inito collision models for hypersonic and non-equilibrium flow simulations. He also works on designing next-generation micro-scale pumps and propulsion systems that exploit heat losses and produce propulsion force and flow motion without requiring pressure gradients. This is done using DSMC simulations and is now extended using machine learning. A thin vane immersed in a rarefied gas with a temperature gradient across its surfaces will produce a force that tends to move the vane from the hot side to the cold side. This is the Crookes radiometer. He has been creating and developing novel concepts in thermal ratchet (rather than using the vanes) pumps and propulsion systems using either an intelligent selection of wall reflection properties or surface morphologies [13].

He was the first to demonstrate that the working mechanism of ratchet pumps and propulsion systems is based on radiometric forces [14]. He was the first researcher to use these pumps for rarefied gas species separation [15]. This topic is exciting in MEMS/NEMS (Micro/nano-electro-mechanical systems) and aerospace communities and impacts technological developments in both fields. The former seeks extra-small scale pumps for miniaturized devices, while the latter is interested in propulsion systems for space applications, like thrust production for space vehicles and orbit control of lightweight satellites. 

In addition to his research in rarefied gas dynamics, he works on bio-inspired techniques to mitigate the destructive impacts of cavitation on the performance of hydraulic machinery. He recently worked on wavy leading hydrofoils inspired by a particular Humpback whale species [16]. He showed that the cavitation weakens on the modified geometry, delaying the stall. He also used hybrid surface wettability to control the devastating effects of cavitation [17].

Additionally, he works on novel subgrid-scale (SGS) models in the large eddy simulation (LES) approach for turbulent flows. For the first time, various modern SGS, such as modulated gradient (MG) and anisotropic minimum dissipation (AMD) models, were considered, modified, and implemented in the OpenFOAM framework [18],[19].

Scopus Profile https://www.scopus.com/authid/detail.uri?authorId=24471770600

Scholar Profile: https://scholar.google.com/citations?hl=en&user=AWKLce4AAAAJ&view_op=list_works&sortby=pubdate

3. Direct simulation Monte Carlo: https://en.wikipedia.org/wiki/Direct_simulation_Monte_Carlo

4. Roohi, Ehsan; Stefanov, Stefan (2016). “Collision partner selection schemes in DSMC: From micro/Nano flows to hypersonic flows”: https://www.sciencedirect.com/science/article/abs/pii/S0370157316302344 Physics Reports. 656: 1–38. Bibcode:2016PhR…656….1R. doi:10.1016/j.physrep.2016.08.002.

5. Akhlaghi, Hassan; Roohi, Ehsan; Stefanov, Stefan (2018). “On the consequences of successively repeated collisions in no-time-counter collision scheme in DSMC”: https://www.sciencedirect.com/science/article/abs/pii/S0045793017304139 Computers & Fluids. 161: 23–32. doi:10.1016/j.compfluid.2017.11.005.

6. Stefanov, Stefan K. (January 25, 2011). “On DSMC Calculations of Rarefied Gas Flows with Small Number of Particles in Cells”: http://epubs.siam.org/doi/10.1137/090751864 SIAM Journal on Scientific Computing. 33 (2): 677–702. Bibcode:2011SJSC…33..677S. doi:10.1137/090751864 – via CrossRef.

7. https://pubs.aip.org/aip/pof/article-abstract/27/10/107104/314632/A-novel-simplified-Bernoulli-trials-collision?redirectedFrom=fulltext

8. Roohi, Ehsan; Stefanov, Stefan; Shoja-Sani, Ahmad; Ejraei, Hossein (2018). “A generalized form of the Bernoulli Trial collision scheme in DSMC: Derivation and evaluation”: https://www.sciencedirect.com/science/article/abs/pii/S0021999117307921 Journal of Computational Physics. 354: 476–492. Bibcode:2018JCoPh.354..476R. doi:10.1016/j.jcp.2017.10.033.

9. https://pubs.aip.org/aip/pof/article-abstract/34/1/012010/2845513/A-symmetrized-and-simplified-Bernoulli-trial

10. https://pubs.aip.org/aip/pof/article-abstract/34/9/092003/2844541/A-novel-transient-adaptive-subcell-algorithm-with?redirectedFrom=fulltext

11. Goshayeshi, Bijan; Roohi, Ehsan; Stefanov, Stefan (2015). “DSMC simulation of hypersonic flows using an improved SBT-TAS technique”: https://www.sciencedirect.com/science/article/abs/pii/S0021999115006208Journal of Computational Physics. 303: 28–44. Bibcode:2015JCoPh.303…28G. doi:10.1016/j.jcp.2015.09.027.

12. Scanlon, T.J.; Roohi, E.; White, C.; Darbandi, M.; Reese, J.M. (2010). “An open source, parallel DSMC code for rarefied gas flows in arbitrary geometries”: https://www.sciencedirect.com/science/article/abs/pii/S0045793010001891 Computers & Fluids. 39 (10): 2078–2089. doi:10.1016/j.compfluid.2010.07.014.

13. https://www.cambridge.org/core/journals/journal-of-fluid-mechanics/article/abs/radiometric-flow-in-periodically-patterned-channels-fluid-physics-and-improved-configurations/DA76621385D7DF0C3824B8D3F215FE13

14. https://www.nature.com/articles/srep41412

15. https://www.sciencedirect.com/science/article/abs/pii/S0735193320305881

16. https://www.sciencedirect.com/science/article/abs/pii/S0301932220305243

17. https://www.sciencedirect.com/science/article/abs/pii/S1876107023001578

18. https://www.tandfonline.com/doi/abs/10.1080/14685248.2018.1483078

19. https://www.sciencedirect.com/science/article/abs/pii/S0045793018309368

Awards, Honors and Recognitions

2021 Top 1% researcher in Engineering by ESI (Essential Science Indicators).
2021, 2019 Distinguished Professor in Teaching Quality in Mechanical Engineering, Department of Ferdowsi University of Mashhad
2018 Top 1% reviewer in Engineering, Publon.
2019 Top 5% researcher award in Ferdowsi University of Mashhad.
2019 Best MSc thesis advisor in Aerospace Engineering (student Mr. Ali Lotifan), Iranian Aerospace Association.
2019 Distinguished Young Researcher Award in Mechanical Engineering, Iran Academy of Science
2017 Exemplary Professor, Ferdowsi University of Mashhad, Iran
2017 Distinguished Researcher, Faculty of Engineering, Ferdowsi University of Mashhad, Iran.
2016 Best MSc thesis advisor in Propulsion Engineering (student: Mr. Bijan Goshayeshi), Iranian Aerospace Association

2015 Distinguished Young Researcher, Faculty of Engineering, Ferdowsi University of Mashhad, Iran.
2014 Distinguished Researcher for high-quality research, Ferdowsi University of Mashhad, Iran.
2010 Outstanding Ph.D. Graduate Award, Dean of the University, Sharif University of Technology
2006-2012 Ranked 1st among Ph.D. candidates, Aerospace Department, Sharif University of Technology
2010 Best Ph.D. thesis in Propulsion division at the Aerospace Department, Sharif University of Technology
2004-2006 Ranked 2nd among M.Sc. graduates, Mechanical Engineering Department, Ferdowsi University of Mashhad
2004 Ranked 1st University Entrance Exam, M.Sc. degree in Aerospace Eng.