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Article: Origin and evolution of immersed boundary methods in computational fluid dynamics.

Mittal, Rajat / Seo, Jung Hee

Physical review fluids

2023 Volume 8, Issue 10

Abstract: This article presents the evolutionary history of Immersed Boundary Methods (IBMs), tracing their origins to the very beginning of computational fluid dynamics in the late 1950s all the way to the present day. The article highlights the advancements in ... ...

Abstract	This article presents the evolutionary history of Immersed Boundary Methods (IBMs), tracing their origins to the very beginning of computational fluid dynamics in the late 1950s all the way to the present day. The article highlights the advancements in this simulation methodology over the last fifty years and explores the interplay between IBMs and body-conformal grid (BCG) methods during this time. Drawing upon the author's combined experience of over forty years in this arena, the perspective offered is personal and subjective. By employing a critical and comparative approach through the chronological lens, we hope that this article empowers the reader to understand both the capabilities and limitations of these methods, and to pursue advancements that fill the key gaps and break new ground.
Language	English
Publishing date	2023-10-06
Publishing country	United States
Document type	Journal Article
ISSN	2469-990X
ISSN	2469-990X
DOI	10.1103/physrevfluids.8.100501
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Article ; Online: In

Kuhar, Sharun / Seo, Jung-Hee / Pasricha, Pankaj J / Mittal, Rajat

Journal of the Royal Society, Interface

2024 Volume 21, Issue 210, Page(s) 20230567

Abstract: Pyloric interventions are surgical procedures employed to increase the gastric emptying rate in gastroparesis patients. In this study, we use ... ...

Abstract	Pyloric interventions are surgical procedures employed to increase the gastric emptying rate in gastroparesis patients. In this study, we use an
MeSH term(s)	Humans ; Gastroparesis ; Bile Reflux ; Duodenum ; Computer Simulation
Language	English
Publishing date	2024-01-24
Publishing country	England
Document type	Journal Article ; Research Support, N.I.H., Extramural ; Research Support, U.S. Gov't, Non-P.H.S.
ZDB-ID	2156283-0
ISSN	1742-5662 ; 1742-5689
ISSN (online)	1742-5662
ISSN	1742-5689
DOI	10.1098/rsif.2023.0567
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Article ; Online: Effect of schooling on flow generated sounds from carangiform swimmers.

Zhou, Ji / Seo, Jung-Hee / Mittal, Rajat

Bioinspiration & biomimetics

2024 Volume 19, Issue 3

Abstract: Computational models are used to examine the effect of schooling on flow generated noise from fish swimming using their caudal fins. We simulate the flow as well as the far-field hydrodynamic sound generated by the time-varying pressure loading on these ... ...

Abstract	Computational models are used to examine the effect of schooling on flow generated noise from fish swimming using their caudal fins. We simulate the flow as well as the far-field hydrodynamic sound generated by the time-varying pressure loading on these carangiform swimmers. The effect of the number of swimmers in the school, the relative phase of fin flapping of the swimmers, and their spatial arrangement is examined. The simulations indicate that the phase of the fin flapping is a dominant factor in the total sound radiated into the far-field by a group of swimmers. For small schools, a suitable choice of relative phase between the swimmers can significantly reduce the overall intensity of the sound radiated to the far-field. The relative positioning of the swimmers is also shown to have an impact on the total radiated noise. For a larger school, even highly uncorrelated phases of fin movement between the swimmers in the school are very effective in significantly reducing the overall intensity of sound radiated into the far-field. The implications of these findings for fish ethology as well as the design and operation of bioinspired vehicles are discussed.
MeSH term(s)	Animals ; Biomechanical Phenomena ; Models, Biological ; Fishes ; Swimming ; Schools
Language	English
Publishing date	2024-04-15
Publishing country	England
Document type	Journal Article
ZDB-ID	2235670-8
ISSN	1748-3190 ; 1748-3182
ISSN (online)	1748-3190
ISSN	1748-3182
DOI	10.1088/1748-3190/ad3a4e
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Article ; Online: Improved swimming performance in schooling fish via leading-edge vortex enhancement.

Seo, Jung-Hee / Mittal, Rajat

Bioinspiration & biomimetics

2022 Volume 17, Issue 6

Abstract: The hydrodynamics of schooling fish has been the subject of continued investigation over the last 50 years; fish schools exhibit a variety of arrangements and several distinct mechanisms have been proposed to explain the hydrodynamic benefits of ... ...

Abstract	The hydrodynamics of schooling fish has been the subject of continued investigation over the last 50 years; fish schools exhibit a variety of arrangements and several distinct mechanisms have been proposed to explain the hydrodynamic benefits of schooling. In the current study, we use direct numerical simulations to show that a caudal fin swimmer trailing another similar swimmer can significantly improve its swimming performance by positioning itself such that the wake-induced flow of the leading fish, enhances the leading-edge vortex (LEV) on the fin of the trailing fish. Improvements of up to 12% in both the thrust and efficiency of the trailing fish are possible with this mechanism. The mechanisms underlying these interactional effects are quantitatively analyzed by applying the force partitioning method, a powerful data-driven method that partitions the pressure forces on the fish into mechanistically distinct components. The analysis reveals that the LEV on the fin dominates the overall thrust production for these swimmers and its enhancement therefore provides an effective and robust means for harnessing fish-fish hydrodynamic interactions in a school. In addition to confirming the potential energetic benefits of schooling, the LEV enhancement mechanism could be exploited in coordinated swimming of bioinspired multi-vehicle or multi-foil flapping foil propulsion systems.
MeSH term(s)	Animals ; Swimming ; Biomechanical Phenomena ; Fishes ; Hydrodynamics
Language	English
Publishing date	2022-11-03
Publishing country	England
Document type	Journal Article ; Research Support, U.S. Gov't, Non-P.H.S.
ZDB-ID	2235670-8
ISSN	1748-3190 ; 1748-3182
ISSN (online)	1748-3190
ISSN	1748-3182
DOI	10.1088/1748-3190/ac9bb4
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Article: Computational Modeling of Drug Dissolution in the Human Stomach.

Seo, Jung Hee / Mittal, Rajat

Frontiers in physiology

2022 Volume 12, Page(s) 755997

Abstract: A computational model of drug dissolution in the human stomach is developed to investigate the interaction between gastric flow and orally administrated drug in the form of a solid tablet. The stomach model is derived from the anatomical imaging data and ...

Abstract	A computational model of drug dissolution in the human stomach is developed to investigate the interaction between gastric flow and orally administrated drug in the form of a solid tablet. The stomach model is derived from the anatomical imaging data and the motion and dissolution of the drug in the stomach are modeled via fluid-structure interaction combined with mass transport simulations. The effects of gastric motility and the associated fluid dynamics on the dissolution characteristics are investigated. Two different pill densities are considered to study the effects of the gastric flow as well as the gravitational force on the motion of the pill. The average mass transfer coefficient and the spatial distributions of the dissolved drug concentration are analyzed in detail. The results show that the retropulsive jet and recirculating flow in the antrum generated by the antral contraction wave play an important role in the motion of the pill as well as the transport and mixing of the dissolved drug concentration. It is also found that the gastric flow can increase the dissolution mass flux, especially when there is substantial relative motion between the gastric flow and the pill.
Language	English
Publishing date	2022-01-10
Publishing country	Switzerland
Document type	Journal Article
ZDB-ID	2564217-0
ISSN	1664-042X
ISSN	1664-042X
DOI	10.3389/fphys.2021.755997
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Article: A Three-Year Retrospective Analysis: Do Nutritional and Immunological Indices Predict Postoperative Complications After Rectal Resection?

Philip Sridhar, Rajeevan / Raghunath, Rajat / Ranjan Jesudason, Mark / Mittal, Rohin

Cureus

2024 Volume 16, Issue 3, Page(s) e55700

Abstract: Background Nutritional and immunological indices, such as prognostic nutritional index (PNI), neutrophil-to-lymphocyte ratio (NLR), and platelet-to-lymphocyte ratio (PLR), have been used as predictors of outcomes and survival in a few cancers. However, ... ...

Abstract	Background Nutritional and immunological indices, such as prognostic nutritional index (PNI), neutrophil-to-lymphocyte ratio (NLR), and platelet-to-lymphocyte ratio (PLR), have been used as predictors of outcomes and survival in a few cancers. However, the literature is unclear about their usefulness in predicting postoperative complications in rectal cancer resection operations. Additionally, the prescribed cut-off values as well as the timing of the tests for these indices vary among studies. We aimed to determine the role of PNI, NLR, and PLR in predicting postoperative complications in patients undergoing rectal resection. Methods This is a retrospective analysis from a colorectal unit of a tertiary care teaching hospital. All consecutive patients undergoing rectal resection for rectal cancer between April 2018 and March 2021 were included. PNI, NLR, and PLR were calculated from preoperative blood tests, and all morbidity and mortality within 30 days of operation were considered. Results A total of 202 patients were included. Three patients who did not have the necessary preoperative blood test reports were excluded. Of the remaining 199, 142 (71.4 %) were males. The mean age was 47.3 years. Of the patients, 13.6% (n = 27) had major morbidity (Clavien-Dindo grade 3-5), including one mortality. The mean PNI, NLR, and PLR were 49.9, 4.3, and 230.5, respectively. The mean PNI between the groups (no complication vs. complication) was 49.6 vs. 50.1 (p = 0.46) and the mean NLR between the same groups was 4.7 vs. 3.8, (p = 0.06), and both were not significant. The mean PLR between the groups (256.3 vs. 203.4, p = 0.01) was found to be significant but significance was not elicited when only major complications were considered. Hence, none of the indices were a good predictor of postoperative complications in our study. Conclusion The role of nutritional and immunological indices (PNI, NLR, and PLR) is limited in predicting postoperative morbidity in rectal resection operations.
Language	English
Publishing date	2024-03-07
Publishing country	United States
Document type	Journal Article
ZDB-ID	2747273-5
ISSN	2168-8184
ISSN	2168-8184
DOI	10.7759/cureus.55700
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Article ; Online: Changes in aorta hemodynamics in Left-Right Type 1 bicuspid aortic valve patients after replacement with bioprosthetic valves: An in-silico study.

Bailoor, Shantanu / Seo, Jung-Hee / Schena, Stefano / Mittal, Rajat

PloS one

2024 Volume 19, Issue 4, Page(s) e0301350

Abstract: Bicuspid aortic valve (BAV) is the most common cardiac congenital abnormality with a high rate of concomitant aortic valve and ascending aorta (AAo) pathologic changes throughout the patient's lifetime. The etiology of BAV-related aortopathy was ... ...

Abstract	Bicuspid aortic valve (BAV) is the most common cardiac congenital abnormality with a high rate of concomitant aortic valve and ascending aorta (AAo) pathologic changes throughout the patient's lifetime. The etiology of BAV-related aortopathy was historically believed to be genetic. However, recent studies theorize that adverse hemodynamics secondary to BAVs also contribute to aortopathy, but their precise role, specifically, that of wall shear stress (WSS) magnitude and directionality remains controversial. Moreover, the primary therapeutic option for BAV patients is aortic valve replacement (AVR), but the role of improved post-AVR hemodynamics on aortopathy progression is also not well-understood. To address these issues, this study employs a computational fluid dynamics model to simulate personalized AAo hemodynamics before and after TAVR for a small cohort of 6 Left-Right fused BAV patients. Regional distributions of five hemodynamic metrics, namely, time-averaged wall shear stress (TAWSS) and oscillating shear index (OSI), divergence of wall shear (DWSS), helicity flux integral & endothelial cell activation potential (ECAP), which are hypothesized to be associated with potential aortic injury are computed in the root, proximal and distal ascending aorta. BAVs are characterized by strong, eccentric jets, with peak velocities exceeding 4 m/s and axially circulating flow away from the jets. Such conditions result in focused WSS loading along jet attachment regions on the lumen boundary and weaker, oscillating WSS on other regions. The jet attachment regions also show alternating streaks of positive and negative DWSS, which may increase risk for local tissue stretching. Large WSS magnitudes, strong helical flows and circumferential WSS have been previously implicated in the progression of BAV aortopathy. Post-intervention hemodynamics exhibit weaker, less eccentric jets. Significant reductions are observed in flow helicity, TAWSS and DWSS in localized regions of the proximal AAo. On the other hand, OSI increases post-intervention and ECAP is observed to be low in both pre- and post-intervention scenarios, although significant increases are also observed in this ECAP. These results indicate a significant alleviation of pathological hemodynamics post AVR.
MeSH term(s)	Humans ; Bicuspid Aortic Valve Disease ; Heart Valve Diseases/complications ; Aorta/pathology ; Aortic Valve/physiology ; Hemodynamics/physiology ; Stress, Mechanical
Language	English
Publishing date	2024-04-16
Publishing country	United States
Document type	Journal Article
ZDB-ID	2267670-3
ISSN	1932-6203 ; 1932-6203
ISSN (online)	1932-6203
ISSN	1932-6203
DOI	10.1371/journal.pone.0301350
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Article ; Online: A pilot study of intraoperative application of cooled radiofrequency to reduce post-operative pain following total knee arthroplasty.

Liew, Jonathan / Salmon, Lucy / Mittal, Rajat / Pinczewski, Leo

The Knee

2023 Volume 46, Page(s) 62–70

Abstract: Background: Total Knee Arthroplasty (TKA) is a successful treatment for end stage knee osteoarthritis (OA), but can be associated with significant pain in the early post-operative period. Cooled radiofrequency ablation (CRFA) has reported to reduce knee ...

Abstract	Background: Total Knee Arthroplasty (TKA) is a successful treatment for end stage knee osteoarthritis (OA), but can be associated with significant pain in the early post-operative period. Cooled radiofrequency ablation (CRFA) has reported to reduce knee OA pain by targeting the periarticular nerves. The objective of this pilot study was to assess the effectiveness of intra-operative CRFA for reducing pain and opiate use after TKA. Methods: This was a non randomised prospective study with control group. Participants were sequentially recruited preoperatively and underwent TKA, with CRFA to 6 targeted sites prior to cementing of implants, and were compared to controls who underwent TKA without CRFA. The primary outcome was Day 3 pain scores, and secondary outcomes included week one pain scores, and opiate use up to six weeks post-operative. Results: 17 participants were recruited to the control group and 12 were recruited to the CRFA group. There was no significant difference in demographics or baseline pain scores between the groups. On day 2 the CRFA group had a lower mean pain VAS score of 3.2 compared to 4.4 in the control group (p = 0.03). The mean post operative VAS pain score did not differ between the groups for Day 1, 3, 4, or any other time points up to 6 weeks. There were no significant reduction in opiate use in the CRFA group compared to the control group. There were no adverse events. Conclusion: This study demonstrated intra-operative CRFA was not effective in reducing pain by 50% after TKA in a pilot study.
MeSH term(s)	Humans ; Arthroplasty, Replacement, Knee/adverse effects ; Pilot Projects ; Treatment Outcome ; Prospective Studies ; Knee Joint/surgery ; Osteoarthritis, Knee/complications ; Pain, Postoperative/etiology ; Pain, Postoperative/prevention & control ; Opiate Alkaloids
Chemical Substances	Opiate Alkaloids
Language	English
Publishing date	2023-12-06
Publishing country	Netherlands
Document type	Journal Article
ZDB-ID	1200476-5
ISSN	1873-5800 ; 0968-0160
ISSN (online)	1873-5800
ISSN	0968-0160
DOI	10.1016/j.knee.2023.11.002
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Article ; Online: Outcomes of topography-guided PRK/CXL in keratoconus using the NIDEK CXIII system-"Bharat Protocol" (Pilot study).

Jain, Rajat / Shuaib, Yusra / Mohan, Neha / Mittal, Vikas

Indian journal of ophthalmology

2023 Volume 71, Issue 9, Page(s) 3203–3209

Abstract: Purpose: Outcome of topography-guided excimer laser ablation in conjunction with accelerated, high-fluence cross-linking in corneal ecstatic disease using the NIDEK CXIII equipped with CATz algorithm from the FinalFit software-"Bharat Protocol.": ... ...

Abstract	Purpose: Outcome of topography-guided excimer laser ablation in conjunction with accelerated, high-fluence cross-linking in corneal ecstatic disease using the NIDEK CXIII equipped with CATz algorithm from the FinalFit software-"Bharat Protocol." Methods: Retrospective case record review of 30 eyes of 17 patients of stage 1-3 keratoconus who underwent the procedure was performed. Data collected were for visual acuity, distortion-induced eye pain, and keratometry. Pachymetry, lower order and higher order aberrations, spherical aberrations, and topographic cylinder were documented from by Scheimpflug imaging (Pentacam 70700: Oculus, Wetzlar, Germany). Results: At a minimum follow-up of 6 months (range 6.2-13 months), there was significant improvement in UCVA (P < 0.00001), BCVA (P = 0.0061), decrease in Kmax (P = 0.0349), Ksteep (P < 0.0411), Kflat (P = 0.0099), and pachymetry (P = 0.0001). Significant improvement was also seen in distortion-induced eye pain (27/30 to 2/30; P < 0.00001). A more than two-line improvement in UCVA and BCVA was seen in 23/30 and 17/30 cases, respectively. Ectasia was stabilized in all cases at the last follow-up, and no complications were seen. Conclusions: The "Bharat" Protocol to arrest keratectasia progression and improve corneal regularity is a safe and efficacious alternative as a keratoconus management option. This is the first such study on Nidek Platform for the same.
MeSH term(s)	Humans ; Keratoconus/diagnosis ; Keratoconus/drug therapy ; Keratoconus/surgery ; Pilot Projects ; Eye Pain ; Retrospective Studies ; Cornea/surgery
Language	English
Publishing date	2023-08-01
Publishing country	India
Document type	Journal Article
ZDB-ID	187392-1
ISSN	1998-3689 ; 0301-4738
ISSN (online)	1998-3689
ISSN	0301-4738
DOI	10.4103/IJO.IJO_295_23
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Article ; Online: Reconstructing the pressure field around swimming fish using a physics-informed neural network.

Calicchia, Michael A / Mittal, Rajat / Seo, Jung-Hee / Ni, Rui

The Journal of experimental biology

2023 Volume 226, Issue 8

Abstract: Fish detect predators, flow conditions, environments and each other through pressure signals. Lateral line ablation is often performed to understand the role of pressure sensing. In the present study, we propose a non-invasive method for reconstructing ... ...

Abstract	Fish detect predators, flow conditions, environments and each other through pressure signals. Lateral line ablation is often performed to understand the role of pressure sensing. In the present study, we propose a non-invasive method for reconstructing the instantaneous pressure field sensed by a fish's lateral line system from two-dimensional particle image velocimetry (PIV) measurements. The method uses a physics-informed neural network (PINN) to predict an optimized solution for the pressure field near and on the fish's body that satisfies both the Navier-Stokes equations and the constraints put forward by the PIV measurements. The method was validated using a direct numerical simulation of a swimming mackerel, Scomber scombrus, and was applied to experimental data of a turning zebrafish, Danio rerio. The results demonstrate that this method is relatively insensitive to the spatio-temporal resolution of the PIV measurements and accurately reconstructs the pressure on the fish's body.
MeSH term(s)	Animals ; Zebrafish ; Swimming ; Models, Biological ; Physics ; Neural Networks, Computer
Language	English
Publishing date	2023-04-27
Publishing country	England
Document type	Journal Article ; Research Support, U.S. Gov't, Non-P.H.S.
ZDB-ID	218085-6
ISSN	1477-9145 ; 0022-0949
ISSN (online)	1477-9145
ISSN	0022-0949
DOI	10.1242/jeb.244983
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