Hamid Sadat

• PhD
• Professor (Associate) at University of North Texas

This study conducts a high-fidelity two-way coupled fluid–structure interaction simulations, focusing on a novel perforated elastic vortex generator that is wall-mounted in an open channel with an incoming flow. The response of a perforated elastic vortex generator is investigated across a wide range of dimensionless parameters including dimensionl...

This paper explores the effects of surface texture on noise response and propeller-media interaction for additively manufactured (AM) features of unmanned aerial vehicles (UAV) rotary propellers. The microgeometry nature of material extrusion (ME), molding in additively manufactured molds, and vat polymerization (VP) processes was captured with are...

This paper explores the effects of surface texture on noise response and propeller-media interaction for additively manufactured (AM) features of unmanned aerial vehicles (UAV) rotary propellers. The microgeometry nature of material extrusion (ME), molding in additively manufactured molds, and vat polymerization (VP) processes was captured with are...

In this study, high-fidelity conjugate heat transfer simulations are used to model a micro-channel heat exchanger (MCHE) in a crossflow to study its thermal-hydraulic performance. Three different microchannel geometries, namely circular, triangular, and square with louver-shaped fins, are considered. The local flow field showed a strong coupling be...

All-aluminum microchannel heat exchangers have recently gained popularity in the heating, ventilation, and air conditioning industry. Despite their attractive thermal performance design, these heat exchangers make coils used in automotive, commercial, and residential applications prone to crevice corrosion. This study uses high-fidelity conjugate h...

In this paper, the hydrodynamic performance of KCS (KRISO Container Ship) in the presence of a non-uniform shear current is investigated for the first time using high-fidelity CFD (Computational Fluid Dynamics) simulations. Various shear current strength conditions Frs with different directions were considered and results were compared to the ones...

Transfer and transport of a passive scalar as well as flow structures of unbounded flow over a row of 2, 3, 4 and 5 equispaced identical cylinders at Re = 90 and pitch ratios 1.05D ≤ S ≤ 7D are investigated. Studies are performed through high fidelity simulations using a novel sharp-interface immersed boundary method. Five flow regimes are identifi...

Local and global flow structures as well as transfer and transport of a passive scalar from a circular colony of uniformly distributed cylindrical vegetation are investigated at Re = 2100. The number of cylinders in the colony is varied from 1 to 284 yielding solid fraction of 0.00 < ϕ < 0.65. Three flow regimes are identified: Co-shedding flow reg...

This study investigates the local and global flow structures and mass transfer characteristics for a group of interacting side-by-side cylinders in unbounded flow. Configurations with 2, 3, 4, and 5 members are considered for a range of pitch-ratios ( 1.05 ≤ S / D ≤ 4 ) at the Reynolds number Re = 90. The focus is laid on the time-averaged and inst...

This paper describes a novel 2nd order direct forcing immersed boundary method designed for simulation of 2D and 3D incompressible flow problems with complex immersed boundaries. In this formulation, each cell cut by the immersed boundary (IB) is reshaped to conform to the shape of the IB. IBs are modeled as a series of 2D planes in 3D space that c...

EFD and CFD capability assessment for KCS added power (AP) in head and oblique waves are conducted based on experiments from three facilities using three different model sizes and CFD from five institutes. The analysis includes the standard deviation (SD) in both CFD and EFD to identify facility biases, scale effects and CFD errors for motions, sel...

The noise generated by a quadrotor biplane unmanned aerial system (UAS) is studied computationally for various conditions in terms of the UAS pitch angle, propellers rotating velocity (RPM), and the UAS speed to understand the physics involved in its aeroacoustics and structure-borne noise. The k-ω SST turbulence model and Ffowcs Williams-Hawkings...

The incompressible unsteady Reynolds-averaged Navier-Stokes (URANS) simulations are performed for a free-running container ship in maneuvering conditions: the starboard and portside turning circle simulations with 35° rudder deflection. The validation variables include trajectory, motions, and propeller performances, and the prediction shows accept...

Part 2 reports the validation, local force and local flow study results for the free-running added power simulations whose conditions are the same as the self-propulsion test except for the increased propeller rotational speed and the presence of wave. When targeting the same mean Froude number in the wave condition, the propeller requires the incr...

Verification and validation of computational fluid dynamic simulations are performed at model and full scales for the high-speed littoral combat ship (LCS) surface combatant, including the effects of hook, interceptors, and water-jet propulsion. Predictions of the body force thrust, sinkage, and trim use a speed controller for attaining self-propul...

CFD is assessed for added resistance for KCS (captive test cases 2.10 and 2.11) and course keeping/speed loss for ONRT (free running test cases 3.9/3.12/3.13) in head and oblique waves. The number of submissions were 10, 2, and 8 for test cases 2.10, 2.11, and 3.9/3.12/3.13, respectively. The assessment approach uses both solution and N-version val...

Evaluation is performed of the data used for T2015 test cases for the KCS captive added resistance σAR and ONRT free running course keeping/speed loss in head and oblique waves. For KCS calm water resistance, the individual facility N-order level testing uncertainty is UXi = 1%D and the multiple facility standard deviation based on three institutes...

CFD simulations are conducted to study the wake field behind a marine propeller in open water conditions at various advance coefficients. The local variables (velocity, pressure) and the wake structure characteristics are analyzed extensively using mean, Root Mean Square (RMS) and Fourier analysis of data. The integral variables (forces/moments) an...

Conventional constitutive law-based fluid dynamic models solve the conservation equations of mass and momentum, while kinetic models, such as the well-known lattice Boltzmann method (LBM), solve the propagation and collision processes of the Boltzmann equation-governed particle distribution function (PDF). Such models can provide an a priori modeli...

The blockage effect of an ice mass located close to a rotating propeller is simulated by coupling an Eulerian CFD solver and a Lagrangian Discrete Element Method (DEM) solver. The DEM solver models the ice mass as a collection of particles, located near the propeller. This Eulerian-Lagrangian solver is also coupled to a Multi Body Dynamic (MBD) sol...

In this paper, capabilities of state-of-the-art computational fluid dynamics (CFD) tools in the prediction of the flow-field around a multihull catamaran advancing in straight ahead motion at nonzero drift angles are investigated. CFD estimations have been provided by three research institutes by using their in-house codes: CNR-INM using Xnavis, II...

Predicting maneuverability and stability of a free running ship in following and quartering waves are one of the most important topics to prevent broaching; however current mathematical models show quantitative errors with the experimental data while high-fidelity CFD simulations show quantitative agreement, which provides the opportunity to improv...

The seakeeping ability of ships is one of the aspects that needs to be assessed during the design phase of ships. Traditionally, potential flow calculations and model tests are employed to investigate whether the ship performs according to specified criteria. With the increase of computational power nowadays, advanced computational tools such as Co...

A comprehensive study is conducted to evaluate the heat transfer characteristics of laminar nanofluid flow in an annular tube. Thermo-physical properties of the nanofluid is considered to be variable and for the inner and outer walls, there exists serrated surface roughness. The study focuses on the velocity distribution, friction factor and Nussel...

A statistical approach for computational fluid dynamics (CFD) state-of-the-art (SoA) assessment is presented for specified benchmark test cases and validation variables, based on the combination of solution and N-version verification and validation (V&V). Solution V&V estimates the systematic numerical and modeling errors/uncertainties. N-version v...

The paper presents partitioned tightly coupled fluid-structure interaction (FSI) simulations for composite panel slamming of a high-speed planing hull, including comparison with full-scale experiments. Panels with different layout/stiffness are investigated. Computational fluid dynamics (CFD) is performed using the URANS code CFDShip-Iowa. Computat...

This study investigated the motion responses and flooding behavior of a damaged passenger ship model, using numerical simulations of fluid dynamics and six degrees of freedom motion. The test condition was based on the safe return to port regulations, and the numerical investigation was performed by solving unsteady Reynolds-averaged Navier-Stokes...

The current work presents a partitioned tightly coupled fluid-structure interaction (FSI) simulation of composite panel slamming for a high-speed planing hull including validation with full-scale experiments. The prediction capability of CFD/CSD (computational fluid dynamics/ computational structural dynamics) FSI is shown for composite bottom pane...

This paper presents CFD validation efforts for the high-speed, multihull Delft Catamaran 372 advancing in calm water with steady drift angles. Available experimental data include hydrodynamic loads (from BSHC), sinkage and trim measurements (from BSHC and CNR-INSEAN), and stereo-PIV measurements on several transverse planes (from CNR-INSEAN). Three...

The capabilities of CFD and PF methods are assessed for course keeping of 5415M advancing at a Froude number of 0.248 in irregular waves with JONSWAP spectrum for various wave headings. CFD simulations are conducted with N=32 wave components for the wave headings of 0, 45, 90, 105, 180 deg. An additional beam wave simulation is also conducted using...

Part 1 of this two-part paper presents detailed analysis of the previously conducted ship-ship experiments for Bob Hope and Bobo free to heave and pitch in deep calm water and waves (Van't Veer and Van Engelenburg, 2006). Interactions are quantified, recommendations for future experiments are provided, and the results are used as basis for selectio...

Part 2 of this two-part paper presents URANS ship-ship validation results against the experimental data studied in Part 1. The simulation matrix is designed based on the Part 1 results to focus on most significant effects, as well as to complement the data to further explain the physics involved. Calm water validation results show that the error va...

CFD computations are validated for course keeping and maneuvering of ONRT ship hull advancing at Froude number 0.2 in regular waves. The course keeping computations are conducted for various wave headings (0, 45, 90, 135, 180 deg) with λ/L=1.0 and H/λ=0.02. The maneuvering computation is performed for a turning maneuver with 35 deg rudder deflectio...

Experiments, CFD and PF studies are performed for the KCS containership advancing at Froude number 0.26 in calm water and regular waves. The validation studies are conducted for variable wavelength and wave headings with wave slope of H/λ=1/60. CFD computations are conducted using two solvers CFDShip-Iowa and STAR-CCM+. PF studies are conducted usi...

The capabilities of CFDShip-Iowa V4.5 and V6.2 simulations for wave run-up for single/multiple surface-piercing cylinders in regular waves are assessed in conjunction with the ITTC OEC Workshop on VIV and Wave Run-up held in Nantes, France October 17–18, 2013. Statistical convergence and grid/domain/turbulence model sensitivity studies show uncerta...

The seakeeping ability of ships is one of the aspects that needs to be assessed during the design phase of ships. Traditionally, potential flow calculations and model tests are employed to investigate whether the ship performs according to specified criteria. With the increase of computational power nowadays, advanced computational tools such as Co...

CFD simulations are conducted for zero-speed damaged passenger ship SSRC in calm water and waves with 6DOF motions including flooding procedure in calm water, roll decay in calm water and motions in regular beam waves for various wavelengths. The simulations model the 6DOF soft spring experimental mount, the one- and two-room flooding compartment c...

High fidelity CFD/FE FSI (Computational Fluid Dynamics/Finite Element Fluid-Structure Interaction) code development and validation by full-scale experiments is presented, for the analysis of hydrodynamic and structural slamming responses. A fully instrumented 29-foot high speed-planing hull with sterndrive is used. Starboard and port bottom panels...

An overview is provided of CFDShip-Iowa modeling, numerical methods and high performance computing (HPC), including both current V4.5 and V5.5 and next generation V6. Examples for naval architecture highlight capability and needs. High fidelity V6 simulations for ocean engineering and fundamental physics describe increased resolution for analysis o...

An overview is provided of CFDShip-Iowa modeling, numerical methods and high performance computing (HPC), including both current V4.5 and V5.5 and next generation V6. Examples for naval architecture highlight capability and needs. High fidelity V6 simulations for ocean engineering and fundamental physics describe increased resolution for analysis o...

Test cases related to seakeeping are studied in this chapter including heave and pitch with or without surge motion in regular head waves for KVLCC2 and KCS and wave diffraction and roll-decay with forward speed for DTMB 5415. For seakeeping, the total average error is E = 23 %D, comparable to the average error for previous seakeeping predictions....

Computational fluid dynamics for ship hydrodynamics has made monumental progress over the last ten years, which is reaching the milestone of providing first-generation simulation-based design tools with vast capabilities for model- and full-scale simulations and optimization. This is due to the enabling technologies such as free surface tracking/ca...

The KVLCC2 tanker in fully-loaded condition free to heave and pitch at Froude number 0.142 in three head wave-ship length ratios (0.6, 1.1 and 1.6) is simulated by CFDSHIP-IOWA V4.5. The detailed phenomena of nominal wake behaving in waves are studied by analyzing the velocity and vorticity distribution, and vector field on the propeller plane. The...

CFD simulations of Delft Catamaran ship model at static drift conditions in deep water are conducted. The simulations are for bare hull and ship was either free to sink and trim or fixed. The simulation are performed for wide ranges of Froude numbers (0.3 ≤ Fr ≤ 0.77) and drift angels (0° ≤ β ≤ 30°) using URANS and DES for turbulence modelling. The...

Free running simulations of Delft Catamaran with water-jet propulsion system are conducted for turning and zigzag maneuver. The simulations are conducted either for bare hull with integral force models for water-jet or with actual water-jet with body force impeller defined by pump curves with different slopes. Additionally, captive simulations are...

Predicting ship maneuverings in calm water is an important topic; however, it is very expensive to run numerous maneuvering simulations using CFD. Despite its short computation time, system-based simulations need many captive model tests to estimate the hydrodynamic and rudder maneuvering coefficients used in the system-based mathematical model and...

Computational fluid dynamics for ship hydrodynamics has made monumental progress over the last ten years, which is reaching the milestone of providing first-generation simulation-based design tools with vast capabilities for model-and full-scale simulations and optimization. This is due to the enabling technologies such as free surface tracking/cap...

CFD and system-based simulation are used to predict broaching, surf-riding, and periodic motion for the ONR Tumblehome model, including captive and free model test validation studies. CFD shows close agreement with EFD for calm water resistance, static heel (except for sway force and yaw moment), and static drift (except for roll moment). CFD predi...

The mechanisms of broaching in following regular waves are studied by analysis of free model computations. Simulations of the fully appended ONR Tumblehome model DTMB 5613 are performed with the ship hydrodynamics code CFDShip-Iowa v4.5 and validated against experiments of an auto-piloted, self propelled model ship. Appendages include bilge keels,...

Complementary CFD, towing tank EFD, and nonlinear dynamics approach study of parametric roll for the ONR Tumblehome surface combatant both with and without bilge keels is presented. The investigations without bilge keels include a wide range of conditions. CFD closely agrees with EFD for resistance, sinkage, and trim except for Fr>0.5 which may be...

Stability against capsizing is one of the most fundamental requirements to design a ship. In this research, for the first time, CFD is performed to predict main modes of capsizing. CFD first is conducted to predict parametric rolling for a naval ship. Then CFD study of parametric rolling is extended for prediction of broaching both by using CFD as...

Ship motions in a high sea state can have adverse effects on controllability, cause loss of stability, and ultimately compromise the survivability of the ship. In a broaching event, the ship losses control, naturally turning broadside to the waves, causing a dangerous situation and possibly capsizing. Classical approaches to study broaching rely on...

The present study is concerned with the numerical simulation of free-surface waves and wave induced separation in the presence of an intrusion. The results of several simulations are reported. The first study was performed for a NACA0024 surface piercing hydrofoil over a range of several Froude numbers (0.19, 0.37, 0.55), along with wave breaking a...

The present paper presents the CFD result for a beam wave test case. An ONR tumblehome ship model with bilge keels is used. The beam wave test is for zero forward speed and roll and heave 2DOF with wave slope and wavelength , with the ship length. The problems is solved numerically with an unsteady Reynolds averaged Navier-Stokes approach. The free...

The present simulation deals with numerical calculation of free surface wave induced separation, which is an important phenomenon in naval architecture and offshore engineering problems. Numerical modeling is found to be very effective for studying such complicated flows, because of its lower cost and higher level of producible data. The first simu...

The effect of the asymmetric water entry over a submerged part of a ship on the hydrodynamic impact is investigated numerically. A wedge body is considered and the problem is assumed to be two-dimensional. The results of symmetric and asymmetric impacts are compared. The effect is found significant in the numerical simulation. The maximum hydro-dyn...

The effect of ihe asymmetric water entry over a submerged part of a ship on the hydrodynamic impact is investigated numerically. A wedge body is considered 10 study and the problem is assumed to be two-dimensional. The Results of symmetric and asymmetric impacts are compared together. The effect is found significant in the numerical simulation. The...

These days, tourist submarine industry has become of increasing interest and prosperity. A tourist submarine operating beneath a seaway suffers different undesired motions which may cause difficulty in operability for the vehicle and habitability of its passengers. From this point of view, this paper studies the hydrodynamic problem of submarine op...