Concept Of Effective Diameter Research Articles

Unraveling the motion and deformation characteristics of red blood cells in a deterministic lateral displacement device

Deterministic Lateral Displacement (DLD) device has gained widespread recognition and trusted for filtering blood cells. However, there remains a crucial need to explore the complex interplay between deformable cells and flow within the DLD device to improve its design. This paper presents an approach utilizing a mesoscopic cell-level numerical model based on dissipative particle dynamics to effectively capture this complex phenomenon. To establish the model’s credibility, a series of numerical simulations were conducted and the numerical results were validated with nominal experimental data from the literature. These include single cell stretching experiment, comparisons of the morphological characteristics of cells in DLD, and comparison the specific row-shift fraction of DLD required to initiate the zigzag mode. Additionally, we investigate the effect of cell rigidity, which serves as an indicator of cell health, on average flow velocity, trajectory, and asphericity. Moreover, we extend the existing theory of predicting zigzag mode for solid spherical particles to encompass the behavior of red blood cells. To achieve this, we introduce a new concept of effective diameter and demonstrate its applicability in providing highly accurate predictions across a wide range of conditions.

A new model for water balance estimation on lettuce crops using effective diameter obtained with image analysis

Digital processing and analysis of vegetation cover images allow a precise calculation of some parameters related to crop development, which are linked to the estimation of irrigation requirements of the plants. In this paper, a new methodology for visual monitoring of horticultural crops and computation of the corresponding water needs is presented. The proposed approach is based on the concept of effective diameter, defined as the equivalent diameter of a plant biomass as seen from a top view. It has been applied to a ‘Little Gem’ lettuce crop. The percentage of green cover (PGC), computed by means of a digital processing of captured coverage images, is used to provide accurate estimates of the effective diameter of the plants. Then, this value can be precisely related with some important parameters in agronomy such as root depth, height of the plants, and crop coefficient Kc. Since Kc is an essential parameter in most existing methodologies for water balance estimation, an extensive comparative study on the accuracy of the proposed approach with respect to two alternative methods has been conducted. The first approach is based on PGC and crop density data, while the second is exclusively based on image analysis. The proposed method behaved significantly better in all cases, yielding a coefficient of determination, R2, to the actual Kc values obtained with a Bowen station always above 0.95, and a maximum relative error of only 2.1%. Moreover, the proposed methodology also produced accurate estimates of root depth with R2 values above 0.986 and maximum error below 9%. This approach not only leads to a reduction of water consumption compared to traditional estimation methods, but it also simplifies the required computations and field equipment.

The Effect of Fin Pitch on Fluid Elastic Instability of Tube Arrays Subjected to Cross Flow of Water

Failure of tubes in shell and tube exchangers is attributed to flow induced vibrations of such tubes. There are different excitations mechanisms due to which flow induced vibration occurs and among such mechanisms, fluid elastic instability is the most prominent one as it causes the most violent vibrations and may lead to rapid tube failures within short time. Fluid elastic instability is the fluid–structure interaction phenomenon which occurs when energy input by the fluid force exceeds energy expended in damping. This point is referred as instability threshold and corresponding velocity is referred as critical velocity. Once flow velocity exceeds critical flow velocity, the vibration amplitude increases very rapidly with flow velocity. An experimental program is carried out to determine the critical velocity at instability for plain and finned tube arrays subjected to cross flow of water. The tube array geometry is parallel triangular with cantilever end condition and pitch ratios considered are 2.6 and 2.1. The objective of research is to determine the effect of increase in pitch ratio on instability threshold for plain tube arrays and to assess the effect of addition of fins as well as increase in fin density on instability threshold for finned tube arrays. Plain tube array with two different pitch ratios; 2.1 and 2.6 and finned tube arrays with same pitch ratio; 2.6 but with two different fin pitches; such as fine (10 fpi) and coarse (4 fpi) are considered for the experimentation. Connors’ equation that relates critical velocity at instability to different parameters, on which instability depends, has been used as the basis for analysis and the concept of effective diameter is used for the present investigation. The modal parameters are first suitably modified using natural frequency reduction setup that is already designed and developed to reduce natural frequency and hence to achieve experimental simulation of fluid elastic instability within the limited flow capacity of the pump. The tests are carried out first on plain tube arrays to establish the same as the datum case and results are compared to known results of plain tube arrays and hence the quality of the test rig is also assessed. The fluid elastic vibration tests are then carried out on finned tube arrays with coarse and fine fin pitches and effects of fins and fin pitch on instability threshold are shown. The vibration response of the tube is recorded for each gradually increasing flow rates of water till instability point is reached. The parameters at the instability are then presented in terms of dimensionless parameters to compare them with published results. It is concluded that, arrays with higher pitch ratios are unstable at comparatively higher flow velocities and instability threshold for finned tube arrays is delayed due to addition of the fins. Further, it is concluded that, instability threshold for finned tube arrays with fine fin pitch is delayed compared to coarse fin pitch and hence for increased fin density, instability threshold is delayed. The experimental results in terms of critical velocities obtained for different tube arrays subjected to water cross flow will serve as the base flow rates for air–water cross flow experiments to be conducted in the next phase.

Oxygen temperature variation of a non-premixed oxy-methane flame in a lab-scale slot burner

The effect of temperature variation on the behavior of a non-premixed oxy-methane flame was investigated with a lab-scale slot burner at atmospheric pressure (P∞=1.01325bar). The characteristics of flame behavior were simulated to analyze the flame structure and were observed by measuring the chemiluminescence from OH and CH radicals with a spectrometer and an intensified charge-coupled device (ICCD) camera. Flammable area was estimated by varying the flow velocity from mF=0.02–0.16g/s (i.e., uF=7–50m/s) for methane gas and mOx=0.24–2.71g/s (i.e., uOx=18–117m/s) for oxygen gas. The oxygen temperature at the nozzle exit (TOx) was changed from TOx=300 to 700K. Experimental measurements showed that the flammable area broadened as the oxygen temperature increased. The increase in oxygen temperature was associated with a decrease in the flame length. The concept of effective diameter was used to derive an empirical formula for flame length for use in a combustor design.

Lifted flame behavior of a non-premixed oxy-methane jet in a lab-scale slot burner

The characteristics of oxy-methane flames in atmospheric conditions (298K and 1bar) were studied in a lab-scale slot burner. As a diagnostic tool, OH∗, CH∗, and C2∗ measurements were used to analyze the flame structure. To estimate the flame stabilization, the flow velocity was varied from uF=7–50m/s for methane gas and uOx=10–170m/s for oxygen gas. From the experimental results, the flame stability was enhanced when the slot width became narrower. The flame length increased with increasing fuel quantity, while the lift-off height increased with increase in the fuel jet and oxygen velocity. Using the concept of effective diameter, an empirical formula for flame length was suggested for use in a combustor design.

Influence of nozzle geometry on the near-field structure of a highly underexpanded sonic jet

Abstract Detailed near-field structures of highly underexpanded sonic free jets have been investigated with the help of computational fluid dynamics. Two-dimensional, axisymmetric Euler equations have been chosen to predict the underexpanded jets, and the third-order total variation diminishing finite-difference scheme has been applied to solve the system of governing equations numerically. Several different nozzles have been employed to investigate the influence of the nozzle geometry on the near-field structures of highly underexpanded sonic free jets. The results obtained show that the distance from the nozzle exit to the Mach disk is an increasing function of the jet–pressure ratio, which also significantly influences the shape of the jet boundary. The diameter of the Mach disk increases with the jet–pressure ratio, and it is further significantly influenced by the nozzle geometry, unlike the distance of the Mach disk from the nozzle exit. However, such a dependence on the nozzle geometry is no longer found when an effective-diameter concept is taken into account for the flow from a sharp-edged orifice. A good correlation in the diameters of the Mach disk is obtained, so that the near-field structure of highly underexpanded sonic free jets is a unique function of the pressure ratio, regardless of the nozzle geometry.

Study on the analytical solution of the MSA for a one-component two-Yukawa potential in bovine serum albumin—NaC1 aqueous solution

Using the mean spherical approximation (MSA), an explicit analytical equation of state (EOS) with non-dimensional variables for one-component two-Yukawa fluid is established based on the work of Blum, L., and Ubriaco, M., 2000, Molec. Phys., 98, 829. A simple and directly iterative method is found for obtaining an acceptable solution. The strict two-Yukawa EOS is used to correlate the experimental osmotic pressure data of aqueous bovine serum albumin (BSA)-NaCl solutions in the one-component assumption. Considering the experimental error, the correlation results are good, with only one regressed parameter (disperse energy parameter ε). The deviation of correlation is discussed in detail. A concept of effective diameter, which obviously can decrease the deviation of correlation, is given.

Predictions of the uplift response of model belled piles in geogrid-cell-reinforced sand

Breakout factors from a series of laboratory pullout tests on model-belled piles (or enlarged base footings) in geogrid-cell-reinforced sand, which included tests on various model geometries and sand densities, are examined. The concept of effective diameter and effective embedment ratio based on the diameters of both belled piles and geogrid-cell-reinforcement is introduced which provides a pattern of uplift behaviour consistent with previous findings for anchor-type foundations. A unique relationship between effective breakout factor and effective embedment ratio is derived for a given sand density. Experimental breakout factors compare well with predictions from some existing theories for anchor foundations, while a simple approach based on the vertical slip surface model incorporating an uplift coefficient K=0.8√ K P yields close overall agreement with the laboratory data. A hyperbolic relationship is established between pullout load and displacement, which can be used to determine soil stiffness for use in non-linear analyses.

The use of geophysical surveying methods in the detection of natural cavities and mineshafts

Summary The use of geophysical methods for the location of cavities and mineshafts is reviewed in relation to engineering problems at the site investigation stage. Their success is limited by the resolution and penetration achieved by the particular method applied in a given situation. It is shown that no one single geophysical method will provide the answer to all the problems associated with cavity location but considerable improvement can be achieved by the application of several methods to a given problem. It is suggested that for most standard geophysical methods it is possible to detect a cavity whose depth of burial is less than twice its effective diameter. The concept of effective diameter is shown to be of considerable importance since the presence of the cavity or mineshaft does affect the physical properties of the surrounding rock mass and, hence, gives rise to a far larger anomalous zone than that produced by the cavity on its own.

Heat Transfer in Channels Having Rough and Smooth Surfaces

The author proposes a method of comparing the heat transfer coefficients in two channels in which(1) the cross-sectional shape is different;(2) there are different proportions of rough and smooth surfaces;(3) there are different proportions of heated and unheated surfaces.In particular the method applies to experimental results for the system in which a roughened, heated cylinder is placed centrally in a smooth unheated pipe. The effective diameter concept is used to allow for changes in shape, and the heat-transfer boundary conditions are modified to make them similar to the fluid-flow boundary conditions before the comparison is made.