Bluntness Ratio Research Articles

Predicting high-intensity resuscitation needs in injured patients in the post-hemostasis phase of care following intervention.

Best resuscitation practices in the posthemostasis phase of care are poorly defined; this phase of care is characterized by a range of physiologic derangements and multiple therapeutic modalities used to address them. Using a cohort of injured patients who required an immediate intervention in the operating room or angiography suite following arrival to the emergency department, we sought to define high-intensity resuscitation (HIR) in this posthemostasis phase of care; we hypothesized that those who would require HIR could be identified, using only data available at intensive care unit (ICU) admission. Clinical data were extracted for consecutive injured patients (2016-2019) admitted to the ICU following an immediate procedure in the operating room or angiography suite. High-intensity resuscitation thresholds were defined as the top decile of blood product (≥3 units) and/or crystalloid (≥4 L) use in the initial 12 hours of ICU care and/or vasoactive medication use between ICU hours 2 and 12. The primary outcome, HIR, was a composite of any of these modalities. Predictive modeling of HIR was performed using logistic regression with predictor variables selected using Least Absolute Shrinkage and Selection Operator (LASSO) estimation. Model was trained using 70% of the cohort and tested on the remaining 30%; model predictive ability was evaluated using area under receiver operator curves. Six hundred five patients were included. Patients were 79% male, young (median age, 39 years), severely injured (median Injury Severity Score, 26), and an approximately 3:2 ratio of blunt to penetrating mechanisms of injury. A total of 215 (36%) required HIR. Predictors selected by LASSO included: shock index, lactate, base deficit, hematocrit, and INR. The area under receiver operator curve for the LASSO-derived HIR prediction model was 0.82. Intensive care unit admission data can identify subsequent HIR in the posthemostasis phase of care. Use of this model may facilitate triage, nursing ratio determination, and resource allocation. Therapeutic/Care Management; Level IV.

Leading-edge bluntness effects on the hypersonic flow over the double wedge at multiple aft-wedge angles

The present numerical investigation focuses on the leading-edge bluntness effects on the double wedge with varied aft-wedge angles exposed to low enthalpy hypersonic free stream conditions. The bluntness ratio in this study varies, ranging from R/L1 = 0 (sharp leading edge) to R/L1 = 0.577 (maximum allowable bluntness), along with the aft-wedge angle varying between θ2 = 45° and 60°. Noticeably, even a small bluntness ratio can completely change the shock interaction pattern compared to its sharp geometrical counterpart due to a detached leading-edge shock, enlarged separation bubble, and location of various shock waves concerning it. Critical bluntness ratios exist for the low aft-wedge θ2 = 45° angle, but increasing the aft-wedge angle makes the flow field highly unsteady for some bluntness ratios. Nevertheless, these bluntness ratios for such double-wedge configurations are reported using the mean of separation bubble size. Moreover, this work unravels the cause of such unsteadiness for the unsteady flow fields using the spatial-temporal evolution of the wall pressure distribution and fast Fourier transform of the pressure fluctuation signal at the compression corner and supports the deduced observation with the help of energy-based proper orthogonal decomposition. The increased shock–boundary layer interaction strength moves the separation point upstream beyond the junction of cylindrical bluntness and inclined fore-wedge surface, accompanying sudden change in its direction of motion that perturbs the shear layer that set to a self-sustained, highly unsteady flow field.

Demographic, Clinical Features and Outcome Determinants of Thoracic Trauma in Sri Lanka: A Multicentre Prospective Cohort Study.

Prognostic determinants in thoracic trauma are of major public health interest. We intended to describe patterns of thoracic trauma, demographic factors, clinical course, and predictors of outcome in selected tertiary care hospitals in Sri Lanka. A multicentre prospective cohort study was conducted in five leading teaching hospitals from June to September 2017. Patients with thoracic trauma were followed up during the hospital stay. A logistic regression analysis was conducted using in-hospital morbidity as the dichotomous outcome variable. One hundred seventy-one patients were included in the study yielding 1450 (median = 8.5) person-days of observation. Of them, 71.9% (n = 123) were males. The mean age was 45.8 ± 17.9 years. Majority (39.2%, n = 67) were recruited from the National Hospital of Sri Lanka. Automobile accidents were the commonest (62.6%, n = 107), followed by falls (26.9%, n = 46), assaults (8.8%, n = 15), and animal attacks (1.8%, n = 3). The ratio of blunt to penetrating trauma was 5.6 : 1. Injury patterns were rib fractures (80.7%, n = 138), haemothorax (44.4%, n = 76), pneumothorax (44.4%, n = 76), lung contusion (22.8%, n = 39), flail segment (15.8%, n = 27), tracheobronchial trauma (7.0%, n = 12), diaphragmatic injury (2.3%, n = 4), vascular injury (2.3%, n = 4), cardiac contusions (1.1%, n = 2), and oesophageal injury (0.6%, n = 1). Ninety nine (57.9%) had extrathoracic injuries. Majority (63.2%, n = 108) underwent operative management including intercostal tube insertion (60.8%, n = 104), wound exploration (6.4%, n = 11), thoracotomy (4.1%, n = 7), rib reconstruction (4.1%, n = 7), and video-assisted thoracoscopic surgery (2.9%, n = 5). Pneumonia (10.5%, n = 8), bronchopleural fistulae (2.3%, n = 4), tracheaoesophageal fistulae (1.8%, n = 3), empyema (1.2%, n = 2), and myocardial infarction (1.2%, n = 2) were the commonest postoperative complications. The mean hospital stay was 15.6 ± 18.0 days. The in-hospital mortality was 11 (6.4%). The binary logistic regression analysis with five predictors (age, gender, mechanism of injury (automobile/fall/assault), type of trauma (blunt/penetrating), and the presence of extrathoracic injuries) was statistically significant to predict in-hospital morbidity (X2 (6, n = 168) = 13.1; p=0.041), explaining between 7.5% (Cox and Snell R2) and 14.5% (Nagelkerke R2) of variance. The automobile accidents (OR: 2.3, 95% CI = 0.2–26.2) and being males (OR: 2.3, 95% CI = 0.6–9.0) were the strongest predictors of morbidity.

Heat transfer rate and surface pressure measurements in short duration hypersonic flow

ABSTRACTExperiments were carried out with air as the test gas to obtain the surface convective heating rate and surface pressure distribution on blunt and sharp cone models flying at hypersonic speeds. Tests were performed in a hypersonic shock tunnel at two different angles of attack: ${0}^\circ$ and ${5}^\circ$ with angles of rotation $\phi = {0}^\circ, {90}^\circ$, and ${180}^\circ$. The experiments were conducted at a stagnation enthalpy of 1.4MJ/kg, flow Mach number of 6.56 and free stream Reynolds number based on the model length of $9.1 \times {10}^{5}$. The effective test time of the shock tunnel is 3ms. The results obtained for cone model with a bluntness ratio of 0.2 were compared with sharp cone models for $\alpha ={0}^\circ$. The measured stagnation heat transfer value matched well with the theoretical value predicted by the Fay and Riddell correlation and with the CFD results.

Hypersonic flow past a spherically blunted nose cone: A computational study

The present study investigates the aerodynamic characteristics of spherically blunted nose cone at a hypersonic Mach number of 5.8, numerically. The studies are conducted for different combinations of bluntness ratios and semi-cone angles, at zero angle of attack, in order to ascertain the nose cone parameters which provide minimum aerodynamic drag coefficient. The velocity vector shows the flow deceleration near the nose, re-acceleration through the sides as well the formation of recirculation zones. The structure of bow shock formed ahead of the nose as well as shock detachment distance is depicted by the Mach number contours. It is observed that the shock detachment distance follows linearly increasing behaviour with increase in bluntness ratios for all semi-cone angles studied. An empirical expression is developed for the shock detachment distance using the regression analysis, which reveals that it is mainly a function of bluntness ratio. It is observed that the aerodynamics drag coefficient attains a minimum value for smaller, bluntness ratios and semi-angle. Further, the aerodynamic drag coefficient is observed to be a strong function of bluntness ratios for smaller semi-cone angles.

CFD Analysis of the Effect of Surface Contour of Nose Cone of a Space Vehicle on the Thermal Field during Re-Entry

When the space vehicle re-enters the earth’s atmosphere at a tremendous speed the frictional resistance creates enormous heat which may penetrate the vehicle leading to wreckage, if not dissipated to the surrounding. In the present study, CFD analysis of the thermal field generated on the surface of the solid model of the nose cone of the space vehicle is analyzed. Various configurations of the surface contour of the nose cone are considered to mimic the real life situation. The commercial CFD tool SolidWorks Flow Simulation module was used for the analysis. Four different surface contours were considered for the analysis of the temperature generated on its surface. The results indicate that the surface contour and re-entry velocity has a decided effect on the thermal field developed due to frictional resistance. Nose cone with larger half cone angle with small bluntness ratio offers greater resistance and hence lower temperature is generated compared to small half cone angle configuration.

SCF in Isotopic & Orthotropic Plates Part II: Biaxial Load

This is the second of two companion papers which collectively present a comprehensive 3D finite element analysis on stress concentration in isotropic and orthotropic plates. Any design engineer must know the effect of the various parameters on the stress distribution and strength to successfully design a machine element. The following research makes an attempt to study the effect of cutout orientation and bluntness ratio on the Stress Concentration Factor (SCF) of biaxial loaded isotropic and orthotropic plates. ANSYS APDL environment has been used here to carry out the 3D analysis. The bluntness ratio r/R=0.2 is most effective in terms of percentage reduction in SCF as compared to higher bluntness ratios. The percentage reduction in SCF with r/R=0.2 is about 35% for Mat 1 and Mat 3 and about 50% for Mat 2.

SCF in Isotopic & Orthotropic Plates Part I: Uniaxial Load

This is the first of two companion papers which collectively present a comprehensive 3D finite element analysis on stress concentration in isotropic and orthotropic plates. This research investigates the Stress Concentration Factor (SCF) in isotropic and orthotropic plate due to presence of a central cutout having an orientation θ and effect of bluntness ratio. The simulations are carried out by using a 20 node solid structural 3D element in ANSYS APDL. It is established from the simulations that the SCF for Isotropic material are not dependent on material properties, but dependent upon the shape, size, orientation and location of the cut out. For orthotropic material SCF depends on material properties. It increases with increase in Ey/Ex ratio and decreases with increase in µxy.

Similarity Analysis of Pressure Distribution along the Wake Axis of Elliptic Cones

The Effect of freestream velocity and Ellipticity ratio on the similarity distribution of the static pressure along the wake axis of the elliptic cones is presented. A cone of elliptic cross section produces separated flow at the downstream of its base. Within the separated region the flow is observed to be opposite (reverse) to the main outer flow. To obtain the length of reverse flow region, magnitude and location of maximum reverse velocity and re attachment point knowledge of pressure distribution behind a body is essential. Experiments were carried out for three different test section freestream velocities 6m/s, 15m/s and 25 m/s (Reynolds numbers 0.16 x 105, 0.4 x 105 and 0.667 x 105 based on cone effective diameter respectively). Ellipticity ratio 1 and 3 with constant fineness and bluntness ratio of 2.75 and 0.049 respectively were considered for the experiments. A Digital Sensor Array –DSA was used for static pressure measurements. The pressure sensor has the capability of 1 PSI differential pressure range with +/- 0.12% full-scale accuracy. Good similarity in wake axis static pressure distribution is noted for different freestream velocity behind a circular cone. But, Similarity in pressure distribution is not observed along the wake axis of an elliptic cone at tested lower freestream velocity (6 m/s). Keywords: Elliptic Cone, Pressure Coefficient and Similarity Parameter, Wake Pressure

Similarity Analysis of Pressure Distribution along the Wake Axis of Elliptic Cones

The Effect of freestream velocity and Ellipticity ratio on the similarity distribution of the static pressure along the wake axis of the elliptic cones is presented. A cone of elliptic cross section produces separated flow at the downstream of its base. Within the separated region the flow is observed to be opposite (reverse) to the main outer flow. To obtain the length of reverse flow region, magnitude and location of maximum reverse velocity and re attachment point knowledge of pressure distribution behind a body is essential. Experiments were carried out for three different test section freestream velocities 6m/s, 15m/s and 25 m/s (Reynolds numbers 0.16 x 105, 0.4 x 105 and 0.667 x 105 based on cone effective diameter respectively). Ellipticity ratio 1 and 3 with constant fineness and bluntness ratio of 2.75 and 0.049 respectively were considered for the experiments. A Digital Sensor Array -DSA was used for static pressure measurements. The pressure sensor has the capability of 1 PSI differential pressure range with +/- 0.12% full-scale accuracy. Good similarity in wake axis static pressure distribution is noted for different freestream velocity behind a circular cone. But, Similarity in pressure distribution is not observed along the wake axis of an elliptic cone at tested lower freestream velocity (6 m/s).

Effect of Freestream Velocity Disturbances on Hypersonic Vehicles

The behavior of the pressure disturbance field on bodies experiencing an external disturbance in high-speed flight is of considerable interest because it is the surface pressure fluctuation field that applies much of the potential for structural/vibratory loading. Considered here is a quasi-steady method for a vehicle responding to a velocity field disturbance in near proximity to a high-speed vehicle. The quasi-static assumption implies that the structural surface does not need to deform to induce the associated loading, as would be the case in traditional hypersonic panel flutter problems. The effect of hypersonic shock and supersonic postshock environment is explicitly treated in this analysis. Pressure fluctuation fields as derived by this two-step process are compared to direct perturbation of the mean pressure coefficient via the dynamic pressure. Preliminary studies suggest that the simpler mean flow pressure coefficient/dynamic pressure perturbation as compared to the postshock environment method may overpredict the loading pressure by a factor of two for sharp-edged cones and as much as four for blunt (bluntness ratio 5–10%) sphere cones. Predictions from bothmethods lie within the velocimetry bounds for available experimental data, so it is not possible to select between based on data.

An improved energy method for determining Young’s modulus by instrumented indentation using a Berkovich tip

We previously proposed a method for estimating Young’s modulus from instrumented nanoindentation data based on a model assuming that the indenter had a spherical-capped Berkovich geometry to take account of the bluntness effect. The method is now further improved by releasing the constraint on the tip shape, allowing it to have a much broader arbitrariness to range from a conical-tipped shape to a flat-ended shape, whereas the spherical-capped shape is just a special case in between. This method requires two parameters to specify a tip geometry, namely, a volume bluntness ratio Vr and a height bluntness ratio hr. A set of functional relationships correlating nominal hardness/reduced elastic modulus ratio (Hn/Er) and elastic work/total work ratio (We/W) were established based on dimensional analysis and finite element simulations, with each relationship specified by a set of Vr and hr. Young’s modulus of an indented material can be estimated from these relationships. The method was shown to be valid when applied to S45C carbon steel and 6061 aluminum alloy.

Nose Bluntness for Side-Force Control on Circular Cones at High Incidence

An experimental investigation has been car ked out to study the effect of nose bluntness on the characteristics of vortex asymmetry and induced side forces on slender cone models at low speeds. Two cone models with semi-apex angles of 8 and 12 deg were utilized, and on each model nose bluntness was varied up to 20% (based on base diameter).Measurements made consisted of six-component balance loads over a Widerange of Reynolds number from 0.4 x 10(6) to 5.4 x 10(6). The results show that the onset of vortex asymmetry with nose blunting correlates with geometrical parameters and is practically independent of Reynolds number. The (maximum) side-force levels decrease initially up to a certain bluntness ratio, then increase, followed by a gradual decrease for large values of bluntness ratios. This decrease or increase inside-force levels with nose blunting is associated with a corresponding increase or decrease, respectively, in the onset of vortex asymmetry.Whereas the increase in side-force level beyond the first minimum is qualitatively similar to that observed in earlier studies, the present data definitely indicate that there is a progressive decrease inside-force levels to relatively low values for large bluntness ratios,which could form an important design input. The bluntness ratio corresponding to the occurrence of the first minimum in (maximum) side force depends on the cone angle and is nearly independent of Reynolds number.

New relationship between Young's modulus and nonideally sharp indentation parameters

Both analysis and numerical calculations have been carried out to investigate the relationship between Young’s modulus and nonideally sharp indentation parameters. The results confirm that there exists an approximate one-to-one correspondence between the ratio of nominal hardness/reduced Young’s modulus (Hn/Er) and the ratio of elastic work/total work (We/W) for any definite bluntness ratio (Δh/hm) of a nonideally sharp indenter. Based on this relationship, the Young’s modulus of the indented material can be determined just from the values of Hn, We, and W, which are directly measurable quantities in an indentation test.

An epidemiological view of vascular trauma in Western Australia: a 5-year study.

Although Australia encounters vascular injury less frequently than countries such as the USA, the predominance of blunt trauma with associated complex injuries continues to pose problems for clinicians. The present paper reviews Royal Perth Hospital's experience of vascular trauma epidemiology. All individuals who presented to the Royal Perth Hospital (RPH) with a vascular injury between August 1994 and January 2000 were identified from a prospective trauma database. Injuries were classified using the Abbreviated Injury Score (AIS 90 code). The five major vascular injury groups as defined by AIS 90 (neck, thorax, abdomen, upper limb and lower limb) were analysed in turn to determine which injuries were most frequent, what the common causes were, effects of alcohol and drugs, common associated injuries, investigations performed, mortality, proportion of rural vascular trauma with transfer details and lengths of hospital stay. During the study period, 153 patients (1% of total trauma workload) sustained 175 vascular injuries. The commonest causes of injury for each group were stabbing (neck and lower limb), motor vehicle accident (thorax and abdomen) and work machinery (upper limb). Mortality was highest for thoracic injury (14/32; 44%) followed by abdominal injury (10/29; 34%). The ratio of blunt to penetrating vascular trauma is high and is increasing, as is the ratio of truncal to extremity vascular trauma. The most common artery-vein combination injury was to the femoral vessels. The injury patterns emerging from the present study will hopefully help all medical personnel to recognize the potential for vascular injury in a trauma setting.

Longitudinal analysis of the impact of a level 1 trauma center designation at a university hospital

Background: There have been no quantitative, longitudinal studies on the effect of Level 1 Trauma Center (TC) designation on a facility. The purpose of this study was to evaluate the impact of such designation. Study Design: In September 1990, a 416-bed core affiliate hospital of the state medical school system was state-designated as the Level 1 TC for 6 counties. Data collected from five concurrent 1-year periods after TC designation included case number and acuity of condition, length of hospital and ICU stays, preventable death rates, financial coverage, and neurosurgery and orthopaedic volume. No registry data were available before TC designation. Results: While the yearly number of cases remained stable, the overall severity of cases increased coincident with a 50% reduction in overtriage. The need for ICU services increased over 50%. Mean Injury Severity Score increased from 11.0 in year 1 to 13.8 in year 5. There was a 25% to 30% increase in severe neurosurgery injuries and in major orthopaedic trauma. There was no change in the “self-pay” financial category (12% to 16%) or the ratio of blunt to penetrating trauma (90:10). Conclusions: With Level 1 TC designation in a noninner city setting, planners can expect a shift to more severely injured patients, but should not expect an increase in nonpaying patients. Increases in severe injuries will continue to place strain on the ICU. Impact on neurosurgeons and orthopaedic surgeons mandates their support in TC planning.

Fatal trauma: the modal distribution of time to death is a function of patient demographics and regional resources.

Unlike previous studies in an urban environment, this study examines traumatic death in a geographically diverse county in the southwestern United States. All deaths from blunt and penetrating trauma between November 15, 1991, and November 14, 1993, were included. As many as 150 variables were collected on each patient, including time of injury and time of death. Initial identification of cases was through manual review of death records. Information was supplemented by review of hospital records, case reports, and prehospital encounter forms. A total of 710 traumatic deaths were analyzed. Approximately half of the victims, 52%, were pronounced dead at the scene. Of the 48% who were hospitalized, the most frequent mechanism of injury was a fall. Neurologic dysfunction was the most common cause of death. Two distinct peaks of time were found on analysis: 23% of patients died within the first 60 minutes, and 35% of patients died at 24 to 48 hours after injury. Although there appears to continue to be a trimodal distribution of trauma deaths in urban environments, we found the distribution to be bimodal in an environment with a higher ratio of blunt to penetrating trauma.

Estimation of plane strain fracture toughness from circumferentially bluntly notched round-bar specimens

A technique is presented which allows the use of small bluntly notched round-bar specimens without fatigue pre-cracking for the determination of the plane strain fracture toughness of metallic materials. The technique is based on fracture mechanics analysis and the principle of stress concentration factors at the tip of the notch. The error inherent in the fracture toughness calculations, i.e. due to the absence of a sharp crack, can be corrected by introducing a correction factor which is a function of the normalized notch-tip radius. The technique is applied to two metallic alloys for which the plane strain fracture toughness is estimated. Small round-bar specimens having V-notches with different tip-radii have been tested in tension. A comparison of the K IC values calculated using the present technique with those obtained from sharp notches using three standard equations show reasonable agreement between the two values. It is also observed that the standard equations for calculating fracture toughness may be directly used, without any correction, for specimens having a bluntness ratio less than 0.033. The present technique is a quick and economical method with a level of accuracy adequate for many practical design purposes.

Shock tunnel measurements of hypervelocity blunted cone drag

Presented here are results obtained from an investigation into the effects of nose bluntness on slender cone drag in the hypervelocity flight regime. The results indicate that, for small cone angles, the drag of a blunt cone is reasonably well predicted by the Newtonian sine-square law modified for blunt bodies. This suggests the absence of any real gas effects on the total drag. The effect of nose bluntness at the smaller bluntness ratios is relatively small. This is encouraging for the design of a hypervelocity space plane or a centerbody for an axisymmetric scramjet where a slightly blunted nose is required to reduce stagnation point heating. 7 refs.

Laminar heat transfer to blunt cones in high-enthalpy hypervelocity flows

Measurements of heat transfer on spherically blunted cones of various bluntness ratios in high-enthalpy hypervelocity air flows obtained using a free-piston-driven shock tunnel are described. The stagnation enthalpies considered were in the range 14—20-MJ/kg (equivalent to flight speeds 4—6-km/s). The corresponding equilibrium stagnation temperatures were in the range 7000-9000 K. Comparison of measured data showed reasonable agreement with the classical theory of Lees 1 for small bluntness ratios while the large bluntness ratio results compared well with the empirical theory of Griffith and Lewis.4