The paper presents a numerical simulation and analysis of the flow inside a poppet valve. First, the single-phase (liquid) flow is investigated, and an original model is introduced for quantitatively describing the vortex flow. Since an atmospheric outlet pressure produces large negative absolute pressure regions, a two-phase (cavitating) flow analysis is also performed. Both pressure and density distributions inside the cavity are presented, and a comparison with the liquid flow results is performed. It is found that if one defines the cavity radius such that up to this radius the pressure is no larger than the vaporization pressure, then both liquid and cavitating flow models predict the cavity extent. The current effort is based on the application of the recently developed full cavitation model that utilizes the modified Rayleigh-Plesset equations for bubble dynamics.

In this study, effects of serial stenosis on coronary hemodynamics were investigated in the human right coronary artery (RCA) using blood flow analysis. A 3-D model of a serial stenosed RCA was reconstructed based on multislice computerized tomography images. Numerical analysis examined the effect of multiple serial stenoses on the hemodynamic characteristics such as flow separation, pressure drop and FFR. Pressure loss associated with flow expansion after each constriction was large. Overall pressure drop increased from 1700 Pa (12.75 mmHg) at the end diastole to 11000 Pa (82.5 mmHg) at the peak systole. In two stenoses the corresponding pressure gradients werearound 30 mmHg and corresponded to the stenosis with FFR < 0.7 (associated to the sever stenosis). Severe stenosies caused large pressure drops across the throat. Blood flow distal to the stenosis was associated with fluctuations of the wall shear stress and vorticity.

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BackgroundBlood flow analysis of the human right coronary artery (RCA) has been carried out to investigate the effects of serial stenosis on coronary hemodynamics. A 3-D model of a serial stenosed RCA was reconstructed based on multislice computerized tomography images.MethodsA velocity waveform in the proximal RCA and a pressure waveform in the distal RCA of a patient with a severe stenosis were acquired with a catheter delivered wire probe and applied as boundary conditions. The numerical analysis examines closely the effect of a multiple serial stenosis on the hemodynamic characteristics such as flow separation, wall shear stress (WSS) and particle depositions.Results and ConclusionsEnergy loss associated with such flow expansion after each constriction will be large and consequently the pressure drop will be higher. Overall pressure drop increased from 1700 Pa (12.75 mmHg) at the end diastole to 11000 Pa (82.5 mmHg) at the peak systole. At the peak systole the WSS values reached 110 Pa in the stenosis with 28% diameter reduction and 210 Pa in the stenosis with 54% diameter reduction, which is high enough to damage the endothelial cells. However at the end of one cardiac cycle a percent of 1.4% (15 from 1063 particles release at the inlet section) remain inside the stenosed RCA.

The Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) pandemic significantly impacted the general population’s health. At times, the infection has unfavorably influenced pregnancy evolution and the result of birth. However, vertical transmission of the virus is rare and generates controversial discussions. The study aimed to highlight the clinical, laboratory, and imaging findings of pregnant women with confirmed Coronavirus Disease 2019 (COVID-19) with possible vertical transmission and identify possible factors that encourage vertical transmission. Between 1 April 2020 and 31 December 2021, 281 pregnant women diagnosed with COVID-19 gave birth in the Obstetrics and Gynecology Departments of the tertiary unit of County Emergency Clinical Hospital from Timisoara. Three newborns (1.06%) tested positive. The characteristic of these three cases was described as a short series. In two cases, the patients were asymptomatic. In one case, the patient developed a mild form of COVID-19 with a favorable evolution in all cases. We did not identify the presence of smoking history, vaccine before admission, atypical presentation, fever, or chest X-ray abnormalities. We note possible factors that encourage vertical transmission: Pregnancy-induced hypertension, thrombophilia, asymptomatic cough, an asymptomatic or mild form of the disease, a ruptured membrane, and cesarean. The laboratory results highlight the inconstant presence of some changes found in the list of potential predictors of the severity of the infection: Lymphopenia, high values of C-reactive protein, D-dimer, fibrinogen, platelets, Aspartate Aminotransferase, Lactate dehydrogenase, and ferritin. The study’s conclusion of this small group suggests that there may have been an intrauterine infection in late pregnancy and described characteristics of the pregnant women. Possible risk factors that could encourage vertical transmission have been identified.