Morteza Gharib's research while affiliated with California Institute of Technology and other places

Publications (375)

Article
Full-text available
The turbulent boundary layer (TBL) over the hull surface of a water vehicle significantly elevates the drag force on the water vehicle. In this regard, effectively controlling the TBL can lead to a drag reduction (DR) effect and therefore improve the energy efficiency of water transportation. Many DR methods have demonstrated promising DR effects b...
Preprint
The feasibility of performing airborne and ground manipulation, perception, and reconnaissance using wheeled rovers, unmanned aerial vehicles, CubeSats, SmallSats and more have been evaluated before. Among all of these solutions, balloon-based systems possess merits that make them extremely attractive, e.g., a simple operation mechanism and endured...
Preprint
There have been several successful implementations of bio-inspired legged robots that can trot, walk, and hop robustly even in the presence of significant unplanned disturbances. Despite all of these accomplishments, practical control and high-level decision-making algorithms in multi-modal legged systems are overlooked. In nature, animals such as...
Preprint
Mid-Air Helicopter Delivery (MAHD) is a new Entry, Descent and Landing (EDL) architecture to enable in situ mobility for Mars science at lower cost than previous missions. It uses a jetpack to slow down a Mars Science Helicopter (MSH) after separation from the backshell, and reach aerodynamic conditions suitable for helicopter take-off in mid air....
Article
Despite extensive research in multirotor aerodynamics in the recent past, axial descent, specifically the vortex ring state, still poses great challenges for multirotor configurations as this flight stage is typically accompanied by severe losses in rotor thrust and strong thrust fluctuations. This paper presents a parametric study to investigate t...
Conference Paper
View Video Presentation: https://doi.org/10.2514/6.2022-2426.vid Highly three-dimensional vortical structures and flow separation phenomena present on swept back wings result in complex lift, drag, and pitching moment characteristics. While this may create challenges in the traditional aircraft design process, it provides a promising platform for i...
Article
Full-text available
Prior to its successful flights on Mars, the Ingenuity Mars Helicopter system underwent extensive flight dynamics testing in the 25-ft Space Simulator facility, a low pressure environmental chamber at NASA’s Jet Propulsion Laboratory (JPL), which can re-create relevant Martian conditions on Earth. This facility, while large, is not large enough for...
Conference Paper
View Video Presentation: https://doi.org/10.2514/6.2021-2855.vid There is a conceptual difference between Boundary Layer Control (BLC) and Active Flow Control (AFC). The former aims to compensate for frictional losses in the boundary layer, while the latter seeks to exploit instabilities in the flow to alter its character. The momentum coefficient...
Article
The dynamics of a cantilever plate clamped at its trailing edge and placed at a moderate angle (α ≤ 30∘) to a uniform flow are investigated experimentally and numerically, and a large experimental data set is provided. The dynamics are shown to differ significantly from the zero-angle-of-attack case, commonly called the inverted-flag configuration....
Article
Intrinsic frequencies (IFs) derived from arterial waveforms are associated with cardiovascular performance, aging, and prevalent cardiovascular disease (CVD). However, prognostic value of these novel measures is unknown. We hypothesized that IFs are associated with incident CVD risk. Our sample was drawn from the Framingham Heart Study Original, Of...
Conference Paper
Full-text available
Mid-Air Deployment (MAD) of a rotorcraft during Entry, Descent and Landing (EDL) on Mars eliminates the need to carry a propulsion or airbag landing system. This reduces the total mass inside the aeroshell by more than 100 kg and simplifies the aeroshell architecture. MAD’s lighter and simpler design is likely to bring the risk and cost associated...
Article
The manipulation of near-wall turbulent structures in a turbulent boundary layer (TBL) is an effective way to reduce the turbulent frictional drag. This paper demonstrates the effectiveness of a novel approach for the manipulation of near-wall structures in a TBL with Reynolds number (R_eθ) set to 1200. The manipulation is achieved by employing a s...
Preprint
Full-text available
Mid-Air Deployment (MAD) of a rotorcraft during Entry, Descent and Landing (EDL) on Mars eliminates the need to carry a propulsion or airbag landing system. This reduces the total mass inside the aeroshell by more than 100 kg and simplifies the aeroshell architecture. MAD's lighter and simpler design is likely to bring the risk and cost associated...
Conference Paper
Full-text available
Objectives: Pulsatile cardiac action is an energy consuming process. During pulse wave (PW) travel to the periphery, reflection back to the LV occurs. The concept of wave condition number, WCN, provides evidence that energy consumption of cardiac action is minimised when time of return Tr to LV takes a certain percentage of the cardiac cycle T. Our...
Conference Paper
This paper describes a set of measurements taken at the Caltech Lucas Wind Tunnel, along with Computational Fluid Dynamic analyses, on a wing-body configuration. The configuration is designed to produce regions of separation in the juncture where the wing meets the body. Detailed near- and off-body stereo PIV measurements in the juncture flow are c...
Preprint
The dynamics of a cantilever plate clamped at its trailing edge and placed at a moderate angle ($\alpha \leq 30^{\circ}$) to a uniform flow are investigated experimentally and numerically, and a large experimental data set is provided. The dynamics are shown to differ significantly from the zero-angle-of-attack case, commonly called the inverted-fl...
Article
The method of oncotripsy, first proposed in Heyden & Ortiz (Heyden & Ortiz 2016 J. Mech. Phys. Solids92, 164-175 (doi:10.1016/j.jmps.2016.04.016)), exploits aberrations in the material properties and morphology of cancerous cells in order to ablate them selectively by means of tuned low-intensity pulsed ultrasound. We propose the dynamical model of...
Conference Paper
Aerodynamic investigation of multirotor crafts under non-hover conditions plays a vital role in the development of efficient and stable systems. Non-hover conditions include any flight scenario where the craft is no longer subject to to an infinite, stationary and undisturbed fluid. Examples of non-hover conditions are forward-flight, axial descent...
Article
We present a brief account of Anatol Roshko's research and educational contributions to fluid mechanics, focusing on the spirit of his transformative ideas and legacy.
Preprint
The method of oncotripsy, first proposed in [S. Heyden and M. Ortiz (2016). Oncotripsy: Targeting cancer cells selectively via resonant harmonic excitation. Journal of the Mechanics and Physics of Solids, 92:164-175], exploits aberrations in the material properties and morphology of cancerous cells in order to ablate them selectively by means of tu...
Conference Paper
Introduction and Hypothesis: Intrinsic frequencies (IFs) derived from arterial waveforms, representing the dominant instantaneous frequency during systole and diastole, are associated with cardiovascular performance, aging, and prevalent cardiovascular disease (CVD). However, prognostic value of these novel measures in a community-based sample is u...
Article
Honeybees display a unique biolocomotion strategy at the air–water interface. When water’s adhesive force traps them on the surface, their wetted wings lose ability to generate aerodynamic thrust. However, they adequately locomote, reaching a speed up to 3 body lengths·s ⁻¹ . Honeybees use their wetted wings as hydrofoils for their water surface pr...
Article
Ultrasound can be focused into deep tissues with millimeter precision to perform non-invasive ablative therapy for diseases such as cancer. In most cases, this ablation uses high intensity ultrasound to deposit non-selective thermal or mechanical energy at the ultrasound focus, damaging both healthy bystander tissue and cancer cells. Here we descri...
Preprint
Ultrasound can be focused into deep tissues with millimeter precision to perform non-invasive ablative therapy for diseases such as cancer. In most cases, this ablation uses high intensity ultrasound to deposit non-selective thermal or mechanical energy at the ultrasound focus, damaging both healthy bystander tissue and cancer cells. Here we descri...
Article
Full-scale wind tunnel tests were carried out on a Boeing 757 vertical tail equipped with 37 sweeping jet actuators on the starboard side along the rudder hinge line. The tests were performed at the National Full-Scale Aerodynamics Complex (NFAC) 40- by 80-Foot Wind Tunnel (40×80) at NASA Ames Research Center. The model was tested at a nominal airs...
Conference Paper
This paper describes a set of measurements taken at the Caltech Lucas Wind Tunnel, along with Computational Fluid Dynamic analyses, on a wing-body configuration. The configuration is designed to produce regions of separation in the juncture where the wing meets the body. Detailed on- and off-body measurements in the juncture flow are compared with...
Conference Paper
This paper describes a set of measurements taken at the Caltech Lucas Wind Tunnel, along with Computational Fluid Dynamic analyses, on a wing-body configuration. The configuration is designed to produce regions of separation in the juncture where the wing meets the body. Detailed on- and off-body measurements in the juncture flow are compared with...
Article
The experimental optimization of bio-inspired flapping fin trajectories are demonstrated for potential applications as a side or a rear propulsor of an autonomous underwater vehicle. The trajectories are scored based upon their difference from a force set-point and upon their efficiency and are parameterized by 10 variables inspired by fish swimmin...
Conference Paper
A persistent problem in boundary layer experiments has been the inability to experimentally measure close enough to the wall the resolve the near wall region. This can be because a physical probe, like a hot wire anemometer, is larger than the near wall scales or because an optical probe, like laser Doppler velocimetry, lacks the resolution to get...
Article
The stability of a cantilevered elastic sheet in a uniform flow has been studied extensively due to its importance in engineering and its prevalence in natural structures. Varying the flow speed can give rise to a range of dynamics including limit cycle behaviour and chaotic motion of the cantilevered sheet. Recently, the "inverted flag" configurat...
Preprint
The stability of a cantilevered elastic sheet in a uniform flow has been studied extensively due to its importance in engineering and its prevalence in natural structures. Varying the flow speed can give rise to a range of dynamics including limit cycle behaviour and chaotic motion of the cantilevered sheet. Recently, the "inverted flag" configurat...
Conference Paper
Full-text available
Thermal active flow control has been developed to enhance the efficiency of active flow control systems. The actuation concept is derived from gas-dynamics principles, and it is based on thermal control of the air supply. It is shown that higher air supply temperatures result in reduced mass flow rate with no degradation in active flow control perf...
Article
Thermal active flow control has been developed to enhance the efficiency of active flow control systems. The actuation concept is derived from gas-dynamics principles, and it is based on thermal control of the air supply. It is shown that higher air supply temperatures result in reduced mass flow rate with no degradation in active flow control perf...
Article
An innovative schlieren system design is introduced using two off-the-shelf telescopes instead of large, expensive lenses or mirrors. Schlieren is used in combination with a high-speed camera to investigate the internal dynamics of sweeping jet actuators. These devices are of particular interest due to their great success in active flow control app...
Article
Purpose: Childhood cancer survivors are at risk for anthracycline-related cardiac dysfunction, often developing at a time when they are least engaged in long-term survivorship care. New paradigms in survivorship care and chronic disease screening are needed in this population. We compared the accuracy of a novel handheld mHealth platform (Vivio) as...
Article
Aquatic Anisopteran dragonfly larvae achieve respiration and propulsion by repetitive water jets flowing through their anal openings. Previous studies have shown that the tri-leaflet anal valves modulate the emerging jet by varying the opening size. We discovered that the valves are also capable of controlling the opening asymmetry by independent r...
Article
The interaction and coupling between two inverted flags that are placed side-by-side in a uniform flow is investigated in an effort to determine the behavior of systems that are formed by arrays of cantilevered plates. Inverted flags are elastic plates that are free to move at their leading edge and clamped at their trailing edge. We show that plac...
Article
During the flapping motion of a fish's tail, the caudal fin exhibits antero-posterior bending and dorso-ventral bending, the latter of which is referred to as chord-wise bending herein. The impact of chord-wise tip curvature on the hydrodynamic forces for flapping plates is investigated to explore potential mechanisms to improve the maneuverability...
Article
The Fontan procedure for univentricular heart defects creates a unique circulation where all pulmonary blood flow is passively supplied directly from systemic veins. Computational simulations, aimed at optimizing the surgery, have assumed blood to be a Newtonian fluid without evaluating the potential error introduced by this assumption. We compared...
Article
Full-text available
Saint Elmo’s fire and lightning are two known forms of naturally occurring atmospheric pressure plasmas. As a technology, nonthermal plasmas are induced from artificially created electromagnetic or electrostatic fields. Here we report the observation of arguably a unique case of a naturally formed such plasma, created in air at room temperature wit...
Patent
Full-text available
Improved catheter devices for delivery, repositioning and/or percutaneous retrieval of percutaneously implanted heart valves are described, including a medical device handle that provides an array of features helpful in conducting a percutaneous heart valve implantation procedure while variously enabling radial expansion or contraction and/or later...
Article
A comparison between swimming by flapping and by periodic contractions is conducted. Swimming by flapping is approximated as a pitching plate while swimming by periodic contractions is approximated as clapping plates. A direct comparison is made between the two propulsion mechanisms by utilizing a machine that can operate in either a flapping or a...
Patent
Full-text available
Embodiments described herein address the need for improved catheter devices for delivery, repositioning and/or percutaneous retrieval of the percutaneously implanted heart valves. One embodiment employs a plurality of spring-loaded arms releasably engaged with a stent frame for controlling expansion for valve deployment. Another embodiment employs...
Patent
Full-text available
A cardiac assist system using a helical arrangement of contractile bands and a helically-twisting cardiac assist device are disclosed. One embodiment discloses a cardiac assist system comprising at least one contractile elastic band helically arrangement around a periphery of a patient's heart, where upon an actuation the band contracts helically,...
Article
Objective: The study is based on previously reported mathematical analysis of arterial waveform that extracts hidden oscillations in the waveform that we called intrinsic frequencies. The goal of this clinical study was to compare the accuracy of left ventricular ejection fraction derived from intrinsic frequencies noninvasively versus left ventri...
Article
Cantilevered elastic sheets and rods immersed in a steady uniform flow are known to undergo instabilities that give rise to complex dynamics, including limit cycle behaviour and chaotic motion. Recent work has examined their stability in an inverted configuration where the flow impinges on the free end of the cantilever with its clamped edge downst...
Article
The dynamics of a cantilevered elastic sheet, with a uniform steady flow impinging on its clamped end, have been studied widely and provide insight into the stability of flags and biological phenomena. Recent measurements by Kim et al. ( J. Fluid Mech. , vol. 736, 2013, R1) show that reversing the sheet’s orientation, with the flow impinging on its...
Conference Paper
Aquatic Anisopteran dragonfly larva possesses a modified hindgut pump that enables jet propelled locomotion and respiration. In supporting these functions, the associated flows are modulated by a tri-leaflet anal valve. Previous studies on this valve have been limited to showing larva's ability to modulate the aperture size through concurrent movem...
Article
Full-text available
We discuss the performance of commonly available architectural window materials with respect to the accuracy of optical measurements (e.g. metrology from images, particle image velocimetry, direct image correlation, etc). Window samples were examined for flatness/homogeneity and their performance was quantified by their effect on measurements taken...
Article
Insulin resistance is the hallmark of classical type II diabetes. In addition, insulin resistance plays a central role in metabolic syndrome, which astonishingly affects 1 out of 3 adults in North America. The insulin resistance state can precede the manifestation of diabetes and hypertension by years. Insulin resistance is correlated with a low-gr...
Article
Oxygen plasma treatment is introduced herein as a novel post-growth fabrication technique to engineer the macroscopic morphology of hollow carbon nanotube (CNT) pillars. Current fabrication techniques for patterned vertically-aligned CNTs only allow for the production of extruded structures with constant cross-sectional area. Oxygen plasma treatmen...
Article
The reductionist approach has dominated the fields of biology and medicine for nearly a century. Here, we present a systems science approach to the analysis of physiological waveforms in the context of a specific case, cardiovascular physiology. Our goal in this study is to introduce a methodology that allows for novel insight into cardiovascular p...
Article
INTRODUCTION: Increased aortic stiffness is correlated with many clinically adverse cardiovascular outcomes. The “gold standard” quantitative index for arterial stiffness is the pulse wave velocity (PWV). We have developed a new method called the Intrinsic Frequency ( IF ), which views the arterial pressure waveform as a piecewise combination of tw...
Article
Full-text available
We introduce a novel method for fabricating hollow microneedles for transdermal drug delivery using a composite of vertically-aligned carbon nanotubes and polyimide. Patterned bundles of carbon nanotubes are used as a porous scaffold for defining the microneedle geometry. Polyimide resin is wicked through the carbon nanotube scaffold to reinforce t...
Patent
Full-text available
First and second structures are connected by helical fibers. The orientation between the first and second structures are changed, and by doing so, the positions of the helical fibers are correspondingly changed. The position of change of the helical fibers can be used for a pumping effect, or to change some other fluidic characteristics. One other...
Patent
Full-text available
The invention generally relates to carbon nanotube based drug delivery methods, devices, and compositions. More particularly, the invention relates to controlled drug delivery using anchored carbon nanotube arrays.
Article
The fluttering flag instability has been thoroughly studied through experimental, computational and theoretical means. However, each of these studies only considers the boundary conditions where a flagpole or other tethering mechanism precedes the plate in the fluid flow. Under the inverse condition, where the so-called flag is fixed by its downstr...
Patent
Full-text available
Carbon nanotube needles and needle arrays are described in which the precursor pillars are etched by oxygen plasma treatment to provide tapered and/or sharp tip needles. Processes, products by process, and devices incorporating the sharp-tip needles are further described.
Patent
Full-text available
Carbon nanotube needles and needle arrays are described in which the precursor pillars are etched by oxygen plasma treatment to provide tapered and/or sharp-tip needles. Processes, products by process, and devices incorporating the sharp-tip needles are further described.
Article
The physicochemical and droplet impact dynamics of superhydrophobic carbon nanotube arrays are investigated. These superhydrophobic arrays are fabricated simply by exposing the as-grown carbon nanotube arrays to a vacuum annealing treatment at a moderate temperature. This treatment, which allows a significant removal of oxygen adsorbates, leads to...
Article
The cardiovascular system in mammals follows various optimization criteria covering the heart, the vascular network, and the coupling of the two. Through a simple dimensional analysis we arrived at a non-dimensional number (wave condition number) that can predict the optimum wave state in which the left ventricular (LV) pulsatile power (LV workload...
Patent
Full-text available
An expandable stent that can transform between a collapsed state and an expanded state is described. The stent includes a first cross-sectional shape and a second cross-sectional shape. The first cross-sectional shape is a non-convex shape when the stent is in the collapsed state. Alternatively, the second cross-sectional shape is a convex shape wh...
Article
The findings presented herein show that the electronic properties of CVD graphene on nickel can be altered from metallic to semiconducting by introducing oxygen adsorbates via UV/ozone or oxygen plasma treatment. These properties can be partially recovered by removing the oxygen adsorbates via vacuum annealing treatment. The effect of oxidation is...
Article
Full-text available
Previous studies have demonstrated the existence of optimization criteria in the design and development of mammalians cardiovascular systems. Similarities in mammalian arterial wave reflection suggest there are certain design criteria for the optimization of arterial wave dynamics. Inspired by these natural optimization criteria, we investigated th...
Article
Full-text available
Torque generation and flow distribution of a lift-based vertical-axis turbine with an upstream deflecting plate are investigated in water tunnel experiments. The deployment of a deflector in front of a lift-based turbine is a promising approach to increase local flow velocity and enhance energy conversion efficiency without consideration for compli...
Patent
Full-text available
A method of fabricating a graphene oxide material in which oxidation is confined within the graphene layer and that possesses a desired band gap is provided. The method allows specific band gap values to be developed. Additionally, the use of masks is consistent with the method, so intricate configurations can be achieved. The resulting graphene ox...
Article
Full-text available
The dynamics of an inverted flag are investigated experimentally in order to find the conditions under which self-excited flapping can occur. In contrast to a typical flag with a fixed leading edge and a free trailing edge, the inverted flag of our study has a free leading edge and a fixed trailing edge. The behaviour of the inverted flag can be cl...
Article
Sudden death (SD) in young athletes is a shocking and disturbing event with significant societal impact. Previous studies have demonstrated that sudden cardiac death (SCD) is the leading medical cause of SD in athletes. Various structural and pathological cardiovascular abnormalities have identified as the underlying causes of SCD in young athletes...
Article
An impedance pump - also known as Liebau pump - is a simple valveless pump that operates based on the principles of wave propagation and reflection. It has been shown in embryonic zebrafish that a similar mechanism is responsible for the pumping action in the embryonic heart during the early stages before valve formation. Recent studies suggest tha...
Chapter
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The demand for, and consumption of, global energy is continually increasing across a world whose population will grow to nearly 9 billion people in the next couple of years. It is poised to continue its steady increase in the next several decades. The climate change and the decreasing availability of fossil fuels have hastened the development of sa...
Patent
Described is a method and system for fast three-dimensional imaging using defocusing and feature recognition is disclosed. The method comprises acts of capturing a plurality of defocused images of an object on a sensor, identifying segments of interest in each of the plurality of images using a feature recognition algorithm, and matching the segmen...
Article
In this article, we describe a simple method to reversibly tune the wetting properties of vertically aligned carbon nanotube (CNT) arrays. Here, CNT arrays are defined as densely packed multi-walled carbon nanotubes oriented perpendicular to the growth substrate as a result of a growth process by the standard thermal chemical vapor deposition (CVD)...
Article
The effect of an upstream flat deflector on the power output of two counter-rotating straight-bladed vertical-axis wind turbines (VAWTs) was investigated experimentally. Although many studies on the deflector effect have been done for a drag-based Savonius VAWT, there is little information on the performance of a lift-based VAWT with a deflector. I...