Nondimensional Units Research Articles

Experimental investigation of hydrodynamic interaction between a squat submarine operating behind a ship

This article experimentally investigates the hydrodynamic interaction of a squat submarine operating behind a ship in various wave and resistance tests. A 0.625 m long (one-tenth scale) captive model of a squat submarine is constructed along with a 1.5 m Fridsma ship to perform 47 unique experiments in a 4 × 6 × 400 m3 tank located in a towing tank center. The submarine is a new midget-submersible, of Apam-Napat SMSD type, with an L/D ratio below four. Wave and resistance tests are performed for various 2D relative lengths and depths at short-distance conditions. A wave of 0.1 m height and 1.5 m wavelength is used in the wave tests, and different operational velocities of 0.5, 1.0, and 1.5 m/s are used in the resistance tests. In each case, drag and heave forces are recorded and presented for the vessels using non-dimensional units. Finally, outputs are extended to develop 2D contours to estimate the interactional forces in the full domain. Results show that the interaction between surface waves creates a critical zone behind the ship around the 0.75D depth where the submarine drag forces are increased by up to 41%.

Pressure-induced Hydrodynamic Instability in Premixed Methane-Air Slot Flames

ABSTRACT The impact of pressure on the hydrodynamic instability mechanism is investigated in weakly turbulent, lean methane-air premixed slot flames by means of direct numerical simulations (DNS) employing multi-step chemistry and two different species diffusion models. A dedicated set of slot flames at four different pressures, featuring the same hydrodynamic lengthscale in units of flame thickness, is designed such that the Darrieus-Landau instability mechanism is either suppressed or present in the different flames. For the DNS design, a linear stability analysis is conducted to determine the flame stability characteristics and in particular the cutoff length scale of the Darrieus-Landau instability. As the pressure increases, the cutoff length scale decreases significantly in both dimensional and nondimensional units using the flame thickness as a reference. As a result, an increase in pressure promotes the onset and persistence of the Darrieus-Landau (or hydrodynamic) instability in the slot flame configuration considered. The impact of pressure is investigated in terms of flame morphology using well-established hydrodynamic instability markers. Then, the effect of pressure on the flame speed enhancement caused by the instability is assessed and quantified resorting to the global consumption speed concept. In particular, it is found that over the entire flame brush, the curvature skewness is more negative as pressure increases from 1 to 8 atm and the flame speed is increased by a factor that spans from to trough the flame brush.

Introduction to quantitative engineering design methods via controls engineering

AbstractFunctional modeling is an effective method of depicting products in the design process. Using this approach, product architecture, concept generation, and physical modeling all contribute to the design process to generate a result full of quality and functionality. The functional basis approach provides taxonomy of uniform vocabulary to produce function structures with consistent functions (verbs) and flows (nouns). Material and energy flows dominate function structures in the mechanical engineering domain with only a small percentage including signal flows. Research suggests that the signal flow gap is due to the requirement of “carrier” flows of either material or energy to transport the signals between functions. This research suggests that incorporating controls engineering methodologies may increase the number of signal flows in function structures. We show correlations between the functional modeling and controls engineering in four facets: schematic similarities, performance matching through flows, mathematical function creation using bond graphs, and isomorphic matching of the aforementioned characteristics allows for analogical solutions. Controls systems use block diagrams to represent the sequential steps of the system. These block diagrams parallel the function structures of engineering design. Performance metrics between the two domains can be complimentary when decomposed down to nondimensional engineering units. Mathematical functions of the actions in controls systems can resemble the functional basis functions with bond graphs by identifying characteristic behavior of the functions on the flows. Isomorphic matching, using the schematic diagrams, produces analogies based upon similar functionality and target performance metrics. These four similarities bridge the mechanical and electrical domains via the controls domain. We provide concepts and contextualization for the methodology using domain-agnostic examples. We conclude with suggestion of pathways forward for this preliminary research.

Effect of viscosity ratio on the self-sustained instabilities in planar immiscible jets

Previous studies have shown that intermediate surface tension has a counterintuitive destabilizing effect on 2-phase planar jets. Here, the transition process in confined 2D jets of two fluids with varying viscosity ratio is investigated using DNS. Neutral curves for persistent oscillations are found by recording the norm of the velocity residuals in DNS for over 1000 nondimensional time units, or until the signal has reached a constant level in a logarithmic scale - either a converged steady state, or a "statistically steady" oscillatory state. Oscillatory final states are found for all viscosity ratios (0.1-10). For uniform viscosity (m=1), the first bifurcation is through a surface tension-driven global instability. For low viscosity of the outer fluid, there is a mode competition between a steady asymmetric Coanda-type attachment mode and the surface tension-induced mode. At moderate surface tension, the Coanda-type attachment dominates and eventually triggers time-dependent convective bursts. At high surface tension, the surface tension-dominated mode dominates. For high viscosity of the outer fluid, persistent oscillations appear due to a strong convective instability. Finally, the m=1 jet remains unstable far from the inlet when the shear profile is nearly constant. Comparing this to a parallel Couette flow (without inflection points), we show that in both flows, a hidden interfacial mode brought out by surface tension becomes temporally and absolutely unstable in an intermediate Weber and Reynolds regime. An energy analysis of the Couette setup shows that surface tension, although dissipative, induces a velocity field near the interface which extracts energy from the flow through a viscous mechanism. This study highlights the rich dynamics of immiscible planar uniform-density jets, where several self-sustained and convective mechanisms compete depending on the exact parameters.

Strain energy limitations in Monte Carlo Potts modeling of grain growth

Previous literature reports that the Monte Carlo Potts (MCP) method can only reproduce the linear relationship between grain boundary velocity and strain energy driving force expected under ideal grain growth conditions for small values of strain energy. The exact range of strain energy values for which linearity can be reflected in MCP are not defined. To determine this range, a series of simulations are performed using Monte Carlo Potts in both square 2D and cubic 3D geometries using the Moore neighborhood. These simulations consider cases in which strain energy is either the sole driving force for grain growth or coupled with grain boundary curvature. The 2D results show that the strain energy upper bound is approximately 3.5 non-dimensional units. The 3D simulations show that the relationship between grain boundary velocity and strain energy is dependent on grain boundary curvature. Grain boundary curvature can affect the upper bound of the range of strain energy and can impose a lower bound as well, below which grain growth is discontinuous or stagnate. Both 2D and 3D results are dependent on simulation temperature, with simulation temperature capable of altering the lower and upper bounds in 3D. Increasing simulation temperature in 3D decreases both the upper and lower linearity bounds. MCP simulations using simulation temperatures of zero are not suitable for modeling strain energy driving forces, as grain boundary velocity becomes discontinuous with strain energy.

NLSEmagic: Nonlinear Schrödinger equation multi-dimensional Matlab-based GPU-accelerated integrators using compact high-order schemes

We present a simple to use, yet powerful code package called NLSEmagic to numerically integrate the nonlinear Schrödinger equation in one, two, and three dimensions. NLSEmagic is a high-order finite-difference code package which utilizes graphic processing unit (GPU) parallel architectures. The codes running on the GPU are many times faster than their serial counterparts, and are much cheaper to run than on standard parallel clusters. The codes are developed with usability and portability in mind, and therefore are written to interface with MATLAB utilizing custom GPU-enabled C codes with the MEX-compiler interface. The packages are freely distributed, including user manuals and set-up files. Program summaryProgram title: NLSEmagicCatalogue identifier: AEOJ_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEOJ_v1_0.htmlProgram obtainable from: CPC Program Library, Queen’s University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 124453No. of bytes in distributed program, including test data, etc.: 4728604Distribution format: tar.gzProgramming language: C, CUDA, MATLAB.Computer: PC, MAC.Operating system: Windows, MacOS, Linux.Has the code been vectorized or parallelized?: Yes.Number of processors used: Single CPU, number of GPU processors dependent on chosen GPU card (max is currently 3072 cores on GeForce GTX 690).Supplementary material: Setup guide, Installation guide.RAM: Highly dependent on dimensionality and grid size. For typical medium–large problem size in three dimensions, 4GB is sufficient.Keywords: Nonlinear Schröodinger Equation, GPU, high-order finite difference, Bose-Einstien condensates.Classification: 4.3, 7.7.Nature of problem:Integrate solutions of the time-dependent one-, two-, and three-dimensional cubic nonlinear Schrödinger equation.Solution method:The integrators utilize a fully-explicit fourth-order Runge–Kutta scheme in time and both second- and fourth-order differencing in space. The integrators are written to run on NVIDIA GPUs and are interfaced with MATLAB including built-in visualization and analysis tools.Restrictions:The main restriction for the GPU integrators is the amount of RAM on the GPU as the code is currently only designed for running on a single GPU.Unusual features:Ability to visualize real-time simulations through the interaction of MATLAB and the compiled GPU integrators.Additional comments:Setup guide and Installation guide provided. Program has a dedicated web site at www.nlsemagic.com.Running time:A three-dimensional run with a grid dimension of 87×87×203 for 3360 time steps (100 non-dimensional time units) takes about one and a half minutes on a GeForce GTX 580 GPU card.

On Bounded Satellite Motion under Constant Radial Propulsive Acceleration

The Hamiltonian formulation of the constant radial propulsive acceleration problem in nondimensional units reveals that the problem does not depend on any physical parameter. The qualitative description of the integrable flow is given in terms of the energy and the angular momentum, showing that the different regimes are the result of a bifurcation phenomenon. The solution via the Hamilton‐Jacobi equation demonstrates that the elliptic integrals of the three kinds are intrinsic to the problem.

Maximizing dissipation in a turbulent shear flow by optimal control of its initial state

Turbulent shear flows are known to evolve self-similar at sufficiently high Reynolds numbers. In this regime, flow properties remain constant when normalized with local large-scale reference values. Dissipation of turbulent energy occurs at small scales. Thus, controls which increase dissipation levels in a shear flow may lose their effectiveness once the shear flow attains self-similar behavior governed by large-scale motion. In the current work, we investigate the optimal control of kinetic-energy dissipation in a temporally evolving turbulent mixing layer, with controls acting on its initial condition. Gradient-based optimization is used, relying on direct numerical simulations, and adjoint formulations for the determination of the gradients. Focus is on long optimization time windows T up to 160 nondimensional time units. First we investigate the optimal controls which maximize the total energy dissipation over a simulation time window. For increasing T, optimal controls are found to become also optimal for preceding time horizons. Results indicate that these controls facilitate a fast transition of the mixing layer to a self-similar state, which occurs at nondimensional time t≈160–200. We find that the transition Reynolds number at which self-similarity emerges is a factor of 4–5 lower than transition Reynolds numbers reported for uncontrolled temporal mixing layers. Second, we investigate the maximization of the rate of dissipation at the end of the simulation time window. It is observed that dissipation rate can be increased up to two times higher than self-similar dissipation levels. However, at long optimization time windows this leads to a delay of transition to self-similarity. We further find that optimization is strongly nonconvex, and for the second case, we identify two local optima, which are further discussed in terms of differences in coherent structures emerging during the mixing-layer evolution.

Dynamics of Crystal Structure Formation in Spin-Coated Colloidal Films

The spin-coating of colloidal suspensions is an inherently nonequilibrium process that gives rise to highly reproducible, but polycrystalline, films with different symmetries depending on experimental parameters. In this study, we explore the transient dynamics of evaporative colloid spin-coating for the first time, via a combination of high-speed imaging, atomic force microscopy, static photography, and scanning electron microscopy. As the wet colloidal film thins and dries, we observe several symmetry transitions, while at the same time remarkably, the thinning rate (in nondimensional time units) collapses to one universal curve for all rotation rates. We correlate static and dynamic measures of crossovers in ordering regimes, and obtain an estimate of the evaporation rate in the late stage of drying. We conclude that the thinning dynamics controls the local volume fraction and stress profiles, which in turn drives the structural transitions.

A comprehensive parameter study of an active magnetic regenerator using a 2D numerical model

A two-dimensional numerical heat transfer model is used to investigate an active magnetic regenerator (AMR) based on parallel plates of magnetocaloric material. A large range of parameter variations are performed to study the optimal AMR. The parameters varied are the plate and channel thicknesses, cycle frequency and fluid movement. These are cast into the non-dimensional units utilization, porosity and number of transfer units (NTU). The cooling capacity vs. temperature span is mapped as a function of these parameters and each configuration is evaluated through the maximum temperature span and exergy. The results show that the optimal AMR should have a utilization in the range 0.2–1 and an NTU higher than 10 and not necessarily more than 30. It is concluded that parallel plate-based regenerators face significant challenges in terms of manufacturability. However, the benefit of parallel plate regenerators is a very low pressure drop, which is needed for high performance.

The effects of parameter variation on the gaits of passive walking models: simulations and experiments

SUMMARYWe have made a systematic study of the gait of a straight leg planar passive walking model through simulations and experiments. Three normalised parameters, which represent the foot radius, the position of the mass centre and the moment of inertia, are used to characterise the walking model.In the simulation, we have obtained the fixed points and the basins of attraction of the walking models with different parameter combinations by the aid of the cell mapping method. With the results of fixed points, we investigated the effects of parameter variations on the gait descriptors, including step length, period, average speed and energy inefficiency. A model that has a large basin of attraction has been obtained, and it can start walking far from its fixed point. However, the size of the basin of attraction is not a good measurement of robustness. Thus, we proposed floors with random slope angles or stairs with random heights to test robustness. Five hundred times of simulations with 100 non-dimensional time units were implemented for each parameter combination. The times that the walker failed to arrive at the end were recorded. The simulation results showed that the model with a larger foot radius and higher position of mass centre has a lower possibility of falling on uneven floors. A large moment of inertia is helpful for walking on a random slope angle floor, while low values of moment of inertia are good for navigating random stairs.Prototype experiments have validated the simulation results, which showed that models with larger feet have a longer step length and high speed. However, period differences were difficult to obtain in the experiments since the differences were very small. We have tested the sensitivity with the initial conditions of the models with different foot radii on a flat floor, and have also tested the robustness of the models on a floor with random slope angles. The times that the model reached the end of the floor were recorded. The experimental results showed that a large foot radius is good for improving the basin of attraction and robustness on uneven floors. Finally, the exceptions of the experiment are explained.

Fractal dimension of metallic fracture surface

In this study, a complete method of determination of the fractal dimension for fracture surfaces of ferrous alloys has been proposed. This dimension is determined for the vertical profile obtained by the profile technique cross-section. The image of the profile, seen through the microscope coupled with a camera, is recorded in a computer, where numerical processing is performed. For calculation of the same fractal dimension, the fd3 program has been used, which is available through the Internet. The essential element of the method is optimisation concerning microscopic magnification (scale of a length), resolution of the recorded image and selection of the grey level threshold at binarization. The tests for the stability of discretization, which enable minimization of the error of the measurement, have also been carried out. These tests consist in checking the difference in fractal dimensions for the same profile obtained in two different methods of contouring as well as the difference between capacitive, informative and correlative dimensions. In both cases, too big difference suggests that the determined dimension is not reliable. This method allows determination of the fractal dimension with an absolute accuracy of 0.05 in non-dimensional units. The method has been employed in many studies. In this paper the following tests have been presented: a “fractal map” of the fracture surface was made, an influence of the mechanical notch radius in a compact specimen on the fractal dimension of the fracture surface, an influence of the distortion rate on the fractal dimension, an effect of fatigue crack propagation rate on the fractal dimension and influence of the stress-intensity factor on the fractal dimension of the fracture surface. The following materials were examined: Armco iron, P355N steel and 41Cr4 steel in different states after the heat treatment. The measurements have been made for the specimens of the compact type. There was considered an influence of location of the place of measurement on the fractal dimension being determined. The dimension was determined on the profiles lying longwise and crosswise the crack propagation direction. It has been found that the fractal dimension of the fracture surface does not depend on a place of measurement. This suggests, among other things, that a distinction between the places, which were created under conditions of the plane stress, and the places, which were created under conditions of the plane strain state, cannot be made with the help of the fractal dimension. When testing an influence of the radius of the mechanical tip notch on the fractal dimension of a fracture surface, this dimension was determined in the places located at different distances from the tip of the mechanical notch. With respect to the radii up to 1.0 mm, no significant differences in fractal dimensions have been found. The fractal dimensions of the fracture surface for all examined materials were practically the same and they ranged from 2.02 to 2.10. However in some ranges of da/dN rate the dimension was changing inversely proportional to da/dN. Obtained results confirm that fractal dimension do not depend on the investigated material.

Methodology for Multicriteria Decision Making in Highway Asset Management

A methodology is proposed for multicriteria decision making involving trade-off analyses between candidate projects as well as project selection and programming in highway asset management under certainty, risk, and uncertainty. A set of system goals in highway asset management structure was first identified, and relative weights of the system goals were determined. Performance indicators under each goal were identified. Benefits achieved under various system goals as a result of implementing a project are typically measured with noncommensurable units; they need to be converted into nondimensional units so that trade-offs between projects can be measured under equal parameters. Where such conversion processes involve certainty and risk, this paper develops systemwide multiattribute utility functions for individual asset management programs to form the basis of trade-off analyses. Because of the limitation of utility theory for situations under uncertainty, an alternative approach based on Shackle's model was introduced, and corresponding functions for project trade-offs were calibrated. The two sets of functions were collectively termed "systemwide trade-off functions" and used to deal with cases under certainty, risk, and uncertainty. A case study was conducted for systemwide highway project selection using information on candidate projects in past state highway programming in Indiana. Case study results were further compared with actual highway programming practice in Indiana to validate the proposed methodology. High matching rates of at least 85% were achieved for decision making under certainty, risk, and uncertainty. The approach could be adopted by other state transportation agencies for asset management practice.

Bifurcation Behavior of a Superlattice Model

We present a complete description of the stationary and dynamical behavior of semiconductor superlattices in the framework of a discrete drift model by means of numerical continuation, singular perturbation analysis, and bifurcation techniques. The control parameters are the applied DC voltage ($\phi$) and the doping ($\nu$) in nondimensional units. We show that the organizing centers for the long time dynamics are Takens--Bogdanov bifurcation points in a broad range of parameters and we cast our results in a $\phi$-$\nu$ phase diagram. For small values of the doping, the system has only one uniform solution where all the variables are almost equal. For high doping we find multistability corresponding to domain solutions and the stationary solutions may exhibit chaotic spatial behavior. In the intermediate regime of $\nu$ the solution can be time-periodic depending on the bias. The oscillatory regions are related to the appearance and disappearance of Hopf bifurcation tongues which can be sub- or supercritical. These results are in good agreement with most of the experimental observations and also predict new interesting dynamical behavior.

Dry deposition of particles to wave surfaces: I. Mathematical modeling

Previous estimates of dry deposition to water surfaces were generally based on deposition to flat, solid surfaces. This paper examines the effects of waves on dry deposition rates by numerically simulating particle trajectories over wave surfaces. Airflows over two-dimensional sine waves with height-to-length ratios 2 a/ λ=0.1, 0.07, and 0.03 were calculated with a commercial computational fluid dynamics model. Results from the airflow simulations (velocity, kinetic energy, energy dissipation rate, and shear stress) provided inputs for a stochastic particle trajectory model. Particles were released from a height of 300 non-dimensional wall units at different locations along the wave. For those between 1 and 20 μm, deposition was found to be greatest for particles released to the upslope portion of the wave, followed by the trough, crest and downslope. Overall deposition rates were enhanced due to the presence of waves. Increases ranged from 5% ( d p=80 μm) to 100% ( d p=1 μm) for waves with 2 a/ λ=0.07 and 0.1 and were approximately 50% greater ( d p=1−80 μm) for 2 a/ λ=0.03. Deposition rates were enhanced due to increases in impaction and turbulent transport, both of which increase with increasing wave slope. However, an increased slope also produced regions of low or reversed flow in the trough and downslope, which decreased deposition rates. Due to these competing effects with respect to wave slope, deposition rates did not increase monotonically with wave slope.

Unsteady Crossflow Separation Location Measurements on a Maneuvering 6:1 Prolate Spheroid

The crossflow separation of a 6:1 prolate spheroid undergoing transient maneuvers is studied. The dynamic plunge-pitch-roll model mount provides the unique capability to simulate unsteady maneuvers in a wind tunnel. Hot-film sensors are used with constant-temperature anemometers to measure the time-depcndent wall shear at points over the entire model surface. Minima in wall shear are used to indicate separation locations. Steady and unsteady data are presented for two fast maneuvers: a 0-30-deg, 0.33-s(t' = tU /L = 11) ramp pitchup about the model center (pitchup maneuver) and a 0-13.5-deg, 0.25-s (t' = 8.3) pitchup about the model center that simulates the time-dependent sideslip angle of a submarine entering a turning maneuver (submarine maneuver). Data show that, especially at higher angles of attack, significant lags occur in the flowfield during the maneuvers compared with the steady cases. In particular, separation is delayed at all locations of the model by up to a 10-deg higher angle of attack in the unsteady maneuvers compared with the steady data. Equivalently, the separation structure during the unsteady maneuvers lags the steady data by from 1.5 to 3.5 nondimensional time units t'

Energy stability bounds on convective heat transport:mNumerical study

The concept of nonlinear energy stability has recently been extended to deduce bounds on energy dissipation and transport in incompressible flows, even for turbulent flows. In this approach an effective stability condition on ‘‘background’’ flow or temperature profiles is derived, which when satisfied ensures that the profile produces a rigorous upper estimate to the bulk dissipation. Optimization of the test background profiles in search of the lowest upper bounds leads to nonlinear Euler-Lagrange equations for the extremal profile. In this paper, in the context of convective heat transport in the Boussinesq equations, we describe numerical solutions of the Euler-Lagrange equations for the optimal background temperature and present the numerical computation of the implied bounds. @S1063-651X~97!05706-1# PACS number~s!: 47.27.Te, 03.40.Gc, 47.27.Cn, 47.27.Ak The idea that notions of stability—usually reserved for the characterization of static stationary states—may be applied to dynamic, and even turbulent, phenomena has been proposed at various times and in various contexts. The modern concept of spontaneously self-imposed marginal stability was proposed in the context of thermal convection in the 1950s @1#, later resulting in quantitative predictions for the bulk heat transport @2#. More recently, these sentiments have been given a rigorous formulation in the context of the dynamics of incompressible fluids. Building on a mathematical device invented by Hopf @3#, and utilizing a decomposition referred to as the background field method@4,5#, it has now become possible to formulate variational principles for upper bounds on the time averaged rate of heat transport where the key constraint on the background profiles over which the variation takes place is technically identical to a nonlinear energy stability @6# condition. The optimization problem produces nonlinear Euler-Lagrange equations for the ‘‘marginally stable’’ profile yielding the lowest upper bound. Interestingly, in some cases these Euler-Lagrange equations are of the same functional form as those found in Howard’s theory of bounds on flow quantities in statistically stationary states @7#, and with regard to the functional geometry of the constraints further connection has been established with Busse’s multiple boundary layer theory @8# of Howard’s bounds. In this Brief Report we present the results of a numerical study of the solutions of the Euler-Lagrange equations for the optimal background profile. This study represents a practical implementation of the optimal methods developed in Ref. @5#, and it illustrates some of the features that are expected in this kind of analysis. In particular, we observe that the optimal marginally stable profile may exist on different branches of solutions of the Euler-Lagrange equations, with the signal for the qualitative structural change being a change in ‘‘stability’’ of the solution. Consider an incompressible Newtonian fluid confined to the rectangular volume between rigid noslip isothermal plates at z50 and 1. A vertical temperature gradient is imposed, so in the usual nondimensional units the fluid’s velocity vector field u(x,t)5(u 1 ,u 2 ,u 3 ) and temperature field T(x,t) satisfy the Boussinesq equations ]u ]t 1uiiu1ip5sDu1sRakT, ~1!

Electronic structure and optical absorption of ionized donor molecules in a magnetic field: A finite-element approach.

A three-dimensional finite-element scheme is used to calculate the electronic structure of ${\mathrm{H}}_{2}^{+}$ in magnetic fields of arbitrary directions. The result is used to obtain the magnetoabsorption spectrum of ionized donor molecules ${\mathit{D}}_{2}^{+}$ in high-purity n-type semiconductors in the effective-mass approximation. The absorption peak energy as a function of the magnetic field, expressed in nondimensional units, is found to be universal, i.e., independent of the effective mass, donor concentration, compensation, etc. The calculation provides a clear characteristic feature of ${\mathit{D}}_{2}^{+}$. Also, the usefulness and versatility of the finite-element method in electronic-structure calculations are demonstrated.

Myocardial perfusion changes following 1 year of exercise training assessed by thallium-201 circumferential count profiles

The effect of exercise training on myocardial perfusion was assessed using initial and 1-year thallium-201 (TI-201) exercise studies in 56 patients with stable coronary artery disease (CAD). Subjects had been randomized into a trained group participating in supervised exercise three times per week and a control group. Indices (non-dimensional units) based on computer-analyzed circumferential count profile from nine regions of the heart, assessed in three projections, were used to eliminate observer bias and more accurately quantitate TI-201 distribution and 4-hour washout. There was serial improvement of the global distribution count profiles in 21 of 27 (77.8%) of the trained and in 9 of 29 (31.0%) of the control subjects ( p < 0.001). The mean interval change in global initial distribution over the year period was 5 ± 13 (mean ± SD) in the trained and −6 ± 14 in the control groups ( p < 0.003). The mean initial distribution of the trained group had improvement in all nine regions (significant in three), while the control group showed mean improvement in only one of nine regions. Additionally, the trained group showed improvement in the mean washout in five of nine regions (significant in three), while no mean regional washout improvement occurred in the control group. Thus, in this group of patients with stable CAD, exercise training resulted in apparently improved cardiac perfusion evidenced by enhance TI-201 uptake and washout.

Response of left ventricular volume to exercise in man assessed by radionuclide equilibrium angiography.

To assess the effects of exercise on left ventricular volumes we studied 10 normal men, 15 patients with coronary disease who developed angina pectoris during exercise, and 10 patients with known coronary disease who did not develop angina during exercise. Each subject performed supine bicycle exercise under a mobile, single-crystal scintillation camera until angina or fatigue occurred. Technetium-99m bound to human serum albumin was the imaging agent. Data were collected at rest and during the last 2 minutes of each 3-minute stage of exercise and for 10 minutes after exercise. Volumes were calculated by a new radionuclide technique that correlated well with cineangiography and is expressed in nondimensional units. In normal subjects, the end-diastolic volume (EDV) at rest was not different from that a peak exercise. The end-systolic volume (ESV) decreased at peak exercise. ESV decreased progressively in all but two of 30 exercise periods. Angina patients had a larger EDV at rest and during chest pain than normals. Angina patients increased their ESV during chest pain resulting in a decreased ejection fraction (EF). All angina patients had a higher ESV during chest pain than during the exercise stage before chest pain. As a group, patients who did not developmore » angina had a lower EDV at rest and peak exercise than those who did develop angina. We conclude: that the EF increases during exercise due to a decrease in ESV; that the EF in patients with angina decreases because of an increase in ESV; and that the EF in coronary disease patients without angina shows no change because there is no significant change in the ESV. Radionuclide equilibrium angiography may prove useful for assessing EF and volume changes in patients with coronary artery disease.« less