pith. sign in

arxiv: 2605.22648 · v1 · pith:6YD4XMWPnew · submitted 2026-05-21 · ⚛️ physics.flu-dyn

Experimental investigation of twin pulsed jets in a hemispheric elastic cavity

L. S. Merlo , L. Kadem , W. Saleh , H. D. Ng , G. Di Labbio This is my paper

Pith reviewed 2026-05-22 03:44 UTC · model grok-4.3

classification ⚛️ physics.flu-dyn
keywords twin pulsed jetselastic hemispheric cavityvortex ringsflow regimessymmetry breakingwall reboundcardiac fluid dynamicsparticle image velocimetry
0
0 comments X

The pith

Twin pulsed jets in an elastic hemispheric cavity produce three distinct flow regimes depending on spacing and strength.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper experimentally studies interactions between two parallel pulsed jets inside an expanding elastic hemispheric cavity, a setup chosen to resemble fluid flows in heart chambers. Jet formation times from 1 to 5 and spacing ratios from 1.5 to 3.0 are tested while time-resolved particle image velocimetry records the velocity fields. Three flow regimes emerge: an initial short-time decay of the jets, decay upon reaching the wall, and wall rebound that sometimes generates secondary vortices. The twin vortex rings show symmetry breaking, shifts in their trajectories, and wall-induced rebound effects. These patterns carry direct implications for understanding blood motion in healthy atria as well as in conditions involving valve repairs, leaks, or regurgitation.

Core claim

Varying jet spacing and formation time in the elastic cavity produces three distinct regimes: short-time decay, decay at the wall, and wall rebound with or without secondary vortices. The twin vortex rings display symmetry breaking, trajectory shifts, and wall-induced rebound mechanisms under the tested conditions.

What carries the argument

The three flow regimes identified via time-resolved particle image velocimetry for twin parallel pulsed jets in the elastic hemispheric cavity.

If this is right

  • The identified regimes can inform models of jet interactions inside elastic heart chambers during normal atrial filling or after valve interventions.
  • Symmetry breaking and trajectory shifts provide a mechanism to explain irregular flow patterns observed in pathological regurgitation or paravalvular leaks.
  • Wall rebound with secondary vortex formation depends on specific spacing ratios and can alter mixing or pressure loads near elastic boundaries.
  • The experimental parameter space maps how jet strength and separation control the transition between the three regimes.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The same regime sequence may appear in other elastic-walled chambers where multiple pulsed inflows occur, such as certain biological pumps or engineered fluidic devices.
  • Adjusting jet spacing in medical implants could be explored as a way to suppress unwanted secondary vortices.
  • The symmetry-breaking behavior offers a testable signature for validating reduced-order models of multi-jet elastic cavity flows.

Load-bearing premise

The chosen laboratory-scale elastic hemispheric cavity, formation times, and spacing ratios sufficiently reproduce the essential fluid-structure interactions of pulsed jets inside human heart chambers without scale, fluid properties, or boundary differences dominating the results.

What would settle it

Observation of only one or two of the reported regimes, or absence of symmetry breaking and trajectory shifts, in either a matched numerical simulation at cardiac Reynolds numbers or in direct cardiac imaging data would indicate the regimes do not generalize as described.

read the original abstract

This study experimentally examines the impact of spacing between two pulsed jets and their strengths on the fluid dynamics within an elastic hemispherical cavity. Such interactions between multiple pulsed jets are observed in various natural and industrial contexts, including cardiovascular flows, where they occur naturally within the atria or result from medical interventions (e.g., mitral valve repair, mechanical heart valves, paravalvular leaks) or diseases (e.g., aortic or pulmonary valve regurgitation). Fundamentally, these flows usually feature two or more pulsed jets interacting in an expanding, elastic environment. In this investigation, the experimental setup features two parallel pulsed jets entering the cavity, with jet strength varied across five formation times (1, 2, 3, 4, 5) and four spacing ratios (1.5, 2.0, 2.5, 3.0). Time-resolved particle image velocimetry is used to capture the instantaneous velocity fields. The results reveal three distinct flow regimes: short-time decay, decay at the wall, and wall rebound with or without the formation of secondary vortices. These findings uncover rare aspects of twin vortex ring behavior, including symmetry breaking, trajectory shifts, and wall-induced rebound mechanisms, with direct relevance to cardiac fluid dynamics in both healthy and pathological conditions.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 2 minor

Summary. The manuscript experimentally investigates the fluid dynamics of twin pulsed jets entering an elastic hemispheric cavity, varying jet formation times (1–5) and spacing ratios (1.5–3.0). Time-resolved PIV is used to capture instantaneous velocity fields, revealing three flow regimes (short-time decay, decay at the wall, and wall rebound with or without secondary vortices) along with symmetry breaking and trajectory shifts in twin vortex rings. The work claims direct relevance to cardiac fluid dynamics in healthy and pathological conditions involving multiple jets.

Significance. If the observed regimes and mechanisms hold under the reported conditions, the study provides new experimental data on vortex-ring interactions in confined elastic domains, which is relevant to understanding multi-jet flows in cardiovascular contexts. The time-resolved PIV approach is a standard and appropriate method for resolving instantaneous structures in this setup.

major comments (2)
  1. [Abstract] Abstract: the claim of 'direct relevance to cardiac fluid dynamics in both healthy and pathological conditions' requires explicit verification that key dimensionless groups (Re, Womersley number, and wall compliance) in the laboratory setup match those of atrial/ventricular chambers; no such comparison is provided, making the extrapolation a qualitative analogy rather than a quantitatively supported mapping.
  2. [Methods] The description of the elastic cavity (modulus, thickness, and resulting deformation timescales) is not shown to produce physiologically comparable boundary conditions; without this, the wall-rebound and secondary-vortex regimes may be dominated by laboratory-scale effects rather than the intended fluid-structure interaction.
minor comments (2)
  1. Clarify the precise definition of formation time and how it is nondimensionalized in the experimental protocol.
  2. Add quantitative metrics (e.g., trajectory deviation angles or circulation ratios) to support the symmetry-breaking observations rather than relying solely on qualitative description.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the constructive and detailed review of our manuscript. The comments highlight important aspects of strengthening the link between our experimental observations and cardiac fluid dynamics. We address each major comment below and outline the revisions we will make.

read point-by-point responses

  1. Referee: [Abstract] Abstract: the claim of 'direct relevance to cardiac fluid dynamics in both healthy and pathological conditions' requires explicit verification that key dimensionless groups (Re, Womersley number, and wall compliance) in the laboratory setup match those of atrial/ventricular chambers; no such comparison is provided, making the extrapolation a qualitative analogy rather than a quantitatively supported mapping.

    Authors: We agree that an explicit comparison of dimensionless parameters would make the relevance claim more robust. The experimental conditions were selected to produce vortex-ring interactions and wall-induced effects in a regime motivated by cardiac flows (e.g., formation numbers and spacing ratios drawn from literature on atrial and ventricular jets), but the original manuscript did not tabulate the matching values. In the revised version we will add a dedicated paragraph in the Discussion that reports the Reynolds number range (approximately 800–4500), an estimate of the Womersley number based on the driving frequency and cavity radius, and a compliance parameter derived from observed wall deformation under the measured pressure impulse. These will be compared directly to published physiological ranges for healthy and diseased atria/ventricles, while noting that the model remains a simplified analog rather than an exact replica. revision: yes

  2. Referee: [Methods] The description of the elastic cavity (modulus, thickness, and resulting deformation timescales) is not shown to produce physiologically comparable boundary conditions; without this, the wall-rebound and secondary-vortex regimes may be dominated by laboratory-scale effects rather than the intended fluid-structure interaction.

    Authors: This observation is correct; the Methods section currently gives only a qualitative description of the elastic hemisphere. We will expand it to include the measured Young’s modulus of the silicone material, the wall thickness (2.5 mm), and the characteristic deformation timescale obtained from high-speed imaging of the wall response. We will also add a short analysis comparing the ratio of elastic to inertial timescales in the experiment with corresponding ratios reported for cardiac tissue. These additions will allow readers to assess whether the observed rebound and secondary-vortex formation arise from fluid-structure interaction in a physiologically relevant regime. revision: yes

Circularity Check

0 steps flagged

No circularity: purely observational experimental study with no derivations or fitted predictions

full rationale

The paper is an experimental investigation using time-resolved PIV to observe flow regimes in a lab-scale elastic cavity. It reports measured velocity fields, identifies three flow regimes (short-time decay, decay at the wall, wall rebound), and notes symmetry breaking and trajectory shifts. No equations are derived, no parameters are fitted to data then renamed as predictions, and no self-citations are used to justify uniqueness theorems or ansatzes. The cardiac relevance is presented as contextual motivation and qualitative analogy rather than a derived result from the paper's own chain. All findings reduce directly to the experimental measurements without reduction to prior inputs by construction.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The study is purely experimental and relies on standard assumptions of fluid dynamics without introducing fitted parameters, new theoretical entities, or ad-hoc axioms beyond those implicit in PIV measurements.

axioms (1)
  • domain assumption The working fluid behaves as an incompressible Newtonian fluid under the tested conditions.
    Standard assumption required for interpreting PIV velocity fields in liquid-filled cavities.

pith-pipeline@v0.9.0 · 5776 in / 1396 out tokens · 48140 ms · 2026-05-22T03:44:20.348746+00:00 · methodology

discussion (0)

Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.

Reference graph

Works this paper leans on

30 extracted references · 30 canonical work pages

  1. [1]

    orte -enhanced prop lsion,

    L. . iz, . . hittlese , and J. O. a iri, “ orte -enhanced prop lsion,” J. Fluid Mech., vol. 668, pp. 5–32, Feb. 2011, doi: 10.1017/S0022112010004908

    work page doi:10.1017/s0022112010004908 2011

  2. [2]

    Jet prop lsion in salps T nicata: Thaliacea),

    Q. Bone and E. . Tr eman, “Jet prop lsion in salps T nicata: Thaliacea),” J. Zool., vol. 201, no. 4, pp. 481–506, Dec. 1983, doi: 10.1111/j.1469-7998.1983.tb05071.x

    work page doi:10.1111/j.1469-7998.1983.tb05071.x 1983

  3. [3]

    spects of jet prop lsion in salps,

    L. P. adin, “ spects of jet prop lsion in salps,” Can. J. Zool., vol. 68, no. 4, pp. 765–777, Apr. 1990, doi: 10.1139/z90-111

    work page doi:10.1139/z90-111 1990

  4. [4]

    Comparative jet ake str ct re and s immin performance of salps,

    K. . therland and L. P. adin, “Comparative jet ake str ct re and s immin performance of salps,” J. Exp. Biol. , vol. 213, no. 17, pp. 2967 –2975, Sept. 2010, doi: 10.1242/jeb.041962

    work page doi:10.1242/jeb.041962 2010

  5. [5]

    lti-jet prop lsion or anized clonal development in a colonial siphonophore,

    J. . Costello, . P. Colin, B. J. Gemmell, J. O. a iri, and K. . therland, “ lti-jet prop lsion or anized clonal development in a colonial siphonophore,” Nat. Commun., vol. 6, no. 1, p. 8158, Sept. 2015, doi: 10.1038/ncomms9158

    work page doi:10.1038/ncomms9158 2015

  6. [6]

    P lsatile vorte enerators for lo -speed maneuvering of small underwater vehicles,

    K. ohseni, “P lsatile vorte enerators for lo -speed maneuvering of small underwater vehicles,” Ocean Eng. , vol. 33, no. 16, pp. 2209 –2223, Nov. 2006, doi: 10.1016/j.oceaneng.2005.10.022

    work page doi:10.1016/j.oceaneng.2005.10.022 2006

  7. [7]

    Effects of m ltijet co plin on prop lsive performance in nder ater p lsed jets,

    G. thanassiadis and . P. art, “Effects of m ltijet co plin on prop lsive performance in nder ater p lsed jets,” Phys. Rev. Fluids , vol. 1, no. 3, p. 034501, July 2016, doi: 10.1103/PhysRevFluids.1.034501

    work page doi:10.1103/physrevfluids.1.034501 2016

  8. [8]

    Investi atin vortex ring reconnection in twin parallel pulsed jets: influence of nozzle spacing and stroke ratio,

    T. Chevalier, “Investi atin vortex ring reconnection in twin parallel pulsed jets: influence of nozzle spacing and stroke ratio,” Masters Thesis Concordia Univ. Montr. QC Can., 2023

    work page 2023

  9. [9]

    E perimental st d of vorte rin impin ement on concave hemispherical cavities,

    T. hmed and B. . Erath, “E perimental st d of vorte rin impin ement on concave hemispherical cavities,” J. Fluid Mech. , vol. 967, p. A38, July 2023, doi: 10.1017/jfm.2023.501

    work page doi:10.1017/jfm.2023.501 2023

  10. [10]

    Collision of vorte rin s pon - alls,

    T. . Ne , J. Lon , B. Zan , and . hi, “Collision of vorte rin s pon - alls,” J. Fluid Mech., vol. 899, p. A2, Sept. 2020, doi: 10.1017/jfm.2020.425

    work page doi:10.1017/jfm.2020.425 2020

  11. [11]

    e nolds n m er effect of a vorte rin impinging on a concave hemi-c lindrical shell,

    L. Zhang, G. Li, W. -L. Chen, and . Gao, “ e nolds n m er effect of a vorte rin impinging on a concave hemi-c lindrical shell,” Phys. Fluids, vol. 36, no. 7, p. 075140, July 2024, doi: 10.1063/5.0214319. 19

    work page doi:10.1063/5.0214319 2024

  12. [12]

    orte ring decay in flexible-walled spheroidal confined domains,

    amaee, “ orte ring decay in flexible-walled spheroidal confined domains,” PhD Thesis Okla. Univ., Dec. 2019

    work page 2019

  13. [13]

    o p lmonar valve re r itation after tetralogy of fallot repair changes the flow dynamics in the right ventricle: An in vitro st d ,

    ikhail, G. . La io, . ar ish, and L. Kadem, “ o p lmonar valve re r itation after tetralogy of fallot repair changes the flow dynamics in the right ventricle: An in vitro st d ,” Med. Eng. Phys. , vol. 83, pp. 48 –55, Sept. 2020, doi: 10.1016/j.medengphy.2020.07.014

    work page doi:10.1016/j.medengphy.2020.07.014 2020

  14. [14]

    E perimental investigation of the effect of a MitraClip on left ventricular flow d namics,

    K. Teimo ri, . ar ish, . aleh, . . N , and K. L es, “E perimental investigation of the effect of a MitraClip on left ventricular flow d namics,” Ann. Biomed. Eng. , pp. 1–17, 2025

    work page 2025

  15. [15]

    ed ced-order modeling of left ventricular flow subject to aortic valve re r itation,

    G. i La io and L. Kadem, “ ed ced-order modeling of left ventricular flow subject to aortic valve re r itation,” Phys. Fluids , vol. 31, no. 3, p. 031901, Mar. 2019, doi: 10.1063/1.5083054

    work page doi:10.1063/1.5083054 2019

  16. [16]

    aterial transport in the left ventricle ith aortic valve re r itation,

    G. i La io, J. étel, and L. Kadem, “ aterial transport in the left ventricle ith aortic valve re r itation,” Phys. Rev. Fluids , vol. 3, no. 11, p. 113101, Nov. 2018, doi: 10.1103/PhysRevFluids.3.113101

    work page doi:10.1103/physrevfluids.3.113101 2018

  17. [17]

    niversal time scale for vorte rin formation,

    Ghari , E. am od, and K. hariff, “ niversal time scale for vorte rin formation,” J. Fluid Mech., vol. 360, pp. 121–140, Apr. 1998, doi: 10.1017/S0022112097008410

    work page doi:10.1017/s0022112097008410 1998

  18. [18]

    R. J. Adrian and J. Westerweel, Particle image velocimetry. in Cambridge aerospace series, no. 30. Cambridge: Cambridge Univ. Press, 2011

    work page 2011

  19. [19]

    Raffel, C

    M. Raffel, C. Willert, S. T. Wereley, and J. Kompenhans, Particle image velocimetry: a practical guide, 2nd ed. Berlin: Springer, 2007

    work page 2007

  20. [20]

    PI ncertaint q antification from correlation statistics,

    B. ieneke, “PI ncertaint q antification from correlation statistics,” Meas. Sci. Technol., vol. 26, no. 7, p. 074002, July 2015, doi: 10.1088/0957-0233/26/7/074002

    work page doi:10.1088/0957-0233/26/7/074002 2015

  21. [21]

    efinin coherent vortices o jectivel from the vorticit ,

    G. aller, . adji hasem, . arazmand, and . hn, “ efinin coherent vortices o jectivel from the vorticit ,” J. Fluid Mech. , vol. 795, pp. 136 –173, May 2016, doi: 10.1017/jfm.2016.151

    work page doi:10.1017/jfm.2016.151 2016

  22. [22]

    namic rotation and stretch tensors from a d namic polar decomposition,

    G. aller, “ namic rotation and stretch tensors from a d namic polar decomposition,” J. Mech. Phys. Solids, vol. 86, pp. 70–93, Jan. 2016, doi: 10.1016/j.jmps.2015.10.002

    work page doi:10.1016/j.jmps.2015.10.002 2016

  23. [23]

    Computational Statistics & Data Analysis , author =

    Garcia, “ o st smoothin of ridded data in one and hi her dimensions ith missin val es,” Comput. Stat. Data Anal. , vol. 54, no. 4, pp. 1167 –1178, Apr. 2010, doi: 10.1016/j.csda.2009.09.020

    work page doi:10.1016/j.csda.2009.09.020 2010

  24. [24]

    fast all-in-one method for automated post-processin of PI data,

    Garcia, “ fast all-in-one method for automated post-processin of PI data,” Exp. Fluids, vol. 50, no. 5, pp. 1247–1259, May 2011, doi: 10.1007/s00348-010-0985-y

    work page doi:10.1007/s00348-010-0985-y 2011

  25. [25]

    smoothn,

    Garcia, “smoothn,” TL B Central ile E chan e. [Online]. vaila le: https://www.mathworks.com/matlabcentral/fileexchange/25634-smoothn

    work page

  26. [26]

    orte rin formation for lo e n m ers,

    C. Palacios- orales and . Zenit, “ orte rin formation for lo e n m ers,” Acta Mech., vol. 224, no. 2, pp. 383–397, Feb. 2013, doi: 10.1007/s00707-012-0755-4

    work page doi:10.1007/s00707-012-0755-4 2013

  27. [27]

    lo field prod ced trailin vortices in the vicinit of the ro nd,

    J. K. arve and . J. Perr , “ lo field prod ced trailin vortices in the vicinit of the ro nd,” AIAA J., vol. 9, no. 8, pp. 1659–1660, Aug. 1971, doi: 10.2514/3.6415

    work page doi:10.2514/3.6415 1971

  28. [28]

    orte collision a ainst static and spinnin ro nd c linders: lattice Boltzmann st d ,

    e osis, “ orte collision a ainst static and spinnin ro nd c linders: lattice Boltzmann st d ,” Comput. Fluids , vol. 250, p. 105711, Jan. 2023, doi: 10.1016/j.compfluid.2022.105711

    work page doi:10.1016/j.compfluid.2022.105711 2023

  29. [29]

    orte -dipole impingement with convex and concave o ndaries,

    Kandre, . Y. dkavi, and . . Patil, “ orte -dipole impingement with convex and concave o ndaries,” Phys. Fluids , vol. 36, no. 5, p. 053103, May 2024, doi: 10.1063/5.0200035. 20

    work page doi:10.1063/5.0200035 2024

  30. [30]

    L. S. Merlo, L. Kadem, W. Saleh, H. D. Ng, and G. Di Labbio, Experimental data for Experimental investigation of twin pulsed jets in a hemispheric elastic cavity [Data set], Zenodo (2026), https://doi.org/10.5281/zenodo.19672969

    work page doi:10.5281/zenodo.19672969 2026