scholarly journals Computational Fluid Dynamic Technique for Assessment of How Changing Character of Blood Flow and Different Value of Hct Influence Blood Hemodynamic in Dissected Aorta

Diagnostics ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1866
Author(s):  
Andrzej Polanczyk ◽  
Aleksandra Piechota-Polanczyk ◽  
Ihor Huk ◽  
Christoph Neumayer ◽  
Julia Balcer ◽  
...  
Keyword(s):  
Blood Flow ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Blood Viscosity ◽  
Fluid Dynamic ◽  
Wall Stress ◽  
Acute Type ◽  
Type B ◽  
Type B Dissection

Using computer tomography angiography (CTA) and computational structural analysis, we present a non-invasive method of mass flow rate/velocity and wall stress analysis in type B aortic dissection. Three-dimensional (3D) computer models of the aorta were calculated using pre-operative (baseline) and post-operative CT data from 12 male patients (aged from 51 to 64 years) who were treated for acute type B dissection. A computational fluid dynamics (CFD) technique was used to quantify the displacement forces acting on the aortic wall in the areas of endografts placement. The mass flow rate and wall stress were measured and quantified using the CFD technique. The CFD model indicated the places with a lower value of blood velocity and shear rate, which corelated with higher blood viscosity and a probability of thrombus appearance. Moreover, with the increase in Hct, blood viscosity also increased, while the intensity of blood flow provoked changing viscosity values in these areas. Furthermore, the velocity gradient near the tear surface caused high wall WSS; this could lead to a decreased resistance in the aorta’s wall with further implications to a patient.

scholarly journals Computational Fluid Dynamic Accuracy in Mimicking Changes in Blood Hemodynamics in Patients with Acute Type IIIb Aortic Dissection Treated with TEVAR

2018 ◽  
Vol 8 (8) ◽  
pp. 1309 ◽  
Author(s):  
Andrzej Polanczyk ◽  
Aleksandra Piechota-Polanczyk ◽  
Christoph Domenig ◽  
Josif Nanobachvili ◽  
Ihor Huk ◽  
...  
Keyword(s):  
Blood Flow ◽  
Aortic Dissection ◽  
Flow Rate ◽  
Fluid Dynamic ◽  
3D Models ◽  
Renal Arteries ◽  
Acute Type ◽  
Type Iiib ◽  
Doppler Data ◽  
Flow Through

Background: We aimed to verify the accuracy of the Computational Fluid Dynamics (CFD) algorithm for blood flow reconstruction for type IIIb aortic dissection (TBAD) before and after thoracic endovascular aortic repair (TEVAR). Methods: We made 3D models of the aorta and its branches using pre- and post-operative CT data from five patients treated for TBAD. The CFD technique was used to quantify the displacement forces acting on the aortic wall in the areas of endograft, mass flow rate/velocity and wall shear stress (WSS). Calculated results were verified with ultrasonography (USG-Doppler) data. Results: CFD results indicated that the TEVAR procedure caused a 7-fold improvement in overall blood flow through the aorta (p = 0.0001), which is in line with USG-Doppler data. A comparison of CFD results and USG-Doppler data indicated no significant change in blood flow through the analysed arteries. CFD also showed a significant increase in flow rate for thoracic trunk and renal arteries, which was in accordance with USG-Doppler data (accuracy 90% and 99.9%). Moreover, we observed a significant decrease in WSS values within the whole aorta after TEVAR compared to pre-TEVAR (1.34 ± 0.20 Pa vs. 3.80 ± 0.59 Pa, respectively, p = 0.0001). This decrease was shown by a significant reduction in WSS and WSS contours in the thoracic aorta (from 3.10 ± 0.27 Pa to 1.34 ± 0.11Pa, p = 0.043) and renal arteries (from 4.40 ± 0.25 Pa to 1.50 ± 0.22 Pa p = 0.043). Conclusions: Post-operative remodelling of the aorta after TEVAR for TBAD improved hemodynamic patterns reflected by flow, velocity and WSS with an accuracy of 99%.

A physics-based zero-dimensional model for the mass flow rate of a turbocharger compressor with uniform/distorted inlet condition

2018 ◽  
Vol 20 (6) ◽  
pp. 624-639 ◽  
Author(s):  
Kang Song ◽  
Ben Zhao ◽  
Harold Sun ◽  
Weilin Yi
Keyword(s):  
Flow Field ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Fluid Dynamic ◽  
Dimensional Model ◽  
Inlet Pipe ◽  
External Work ◽  
Compressor Wheel ◽  
Inlet Flow

Turbocharger compressor, when fitted to a vehicle, usually operates with a curved inlet pipe which leads to distorted inlet flow field, hence deteriorating compressor flow capability. During the measurement of compressor performance, turbocharger-engine matching and controller design, the inlet flow field is, however, assumed to be uniform, which deviates from the real-world conditions. Consequently, the overall system performance could be compromised if the inlet distortion effect is ignored. To address this issue, in this article, a turbomachinery physics-based zero-dimensional model was proposed for the mass flow rate of a compressor with distorted inlet flow field due to 90° and 180° bent inlet pipe. The non-uniform flow is approximated as two-zone flow field, similar to parallel compressors, with the total pressure deviation between two zones modeled as a function of the flow velocity and pipe geometry. For each flow zone, the corresponding mass flow rate is estimated by approximating each sub-compressor as an adiabatic nozzle, where the fluid is driven by external work delivered by a compressor wheel governed by Euler’s turbomachinery equation. By including turbomachinery physics and compressor geometry information into the modeling, the model achieves high fidelity in compressor map interpretation and extrapolation, which is validated in experiments and the three-dimensional computational fluid dynamic simulation.

Unsteady Responses of the Impeller of a Centrifugal Compressor Exposed to Pulsating Backpressure

2018 ◽  
Vol 141 (4) ◽  
Author(s):  
Mengying Shu ◽  
Mingyang Yang ◽  
Ricardo F. Martinez-Botas ◽  
Kangyao Deng ◽  
Lei Shi
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Centrifugal Compressor ◽  
Combustion Engine ◽  
Fluid Dynamic ◽  
Flow Behavior ◽  
Three Dimensional ◽  
Intake Manifold ◽  
Unsteady Simulation

The flow in intake manifold of a heavily downsized internal combustion engine has increased levels of unsteadiness due to the reduction of cylinder number and manifold arrangement. The turbocharger compressor is thus exposed to significant pulsating backpressure. This paper studies the response of a centrifugal compressor to this unsteadiness using an experimentally validated numerical method. A computational fluid dynamic (CFD) model with the volute and impeller is established and validated by experimental measurements. Following this, an unsteady three-dimensional (3D) simulation is conducted on a single passage imposed by the pulsating backpressure conditions, which are obtained by one-dimensional (1D) unsteady simulation. The performance of the rotor passage deviates from the steady performance and a hysteresis loop, which encapsulates the steady condition, is formed. Moreover, the unsteadiness of the impeller performance is enhanced as the mass flow rate reduces. The pulsating performance and flow structures near stall are more favorable than those seen at constant backpressure. The flow behavior at points with the same instantaneous mass flow rate is substantially different at different time locations on the pulse. The flow in the impeller is determined by not only the instantaneous boundary condition but also by the evolution history of flow field. This study provides insights in the influence of pulsating backpressure on compressor performance in actual engine situations, from which better turbo-engine matching might be benefited.

scholarly journals Flow Characteristic of Hydraulic Headbox Based on Complementary Pulp Distribution

2015 ◽  
Vol 9 (1) ◽  
pp. 733-738
Author(s):  
Liu Wei ◽  
Ji Xiaohui
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Flow Characteristic ◽  
Fluid Dynamic ◽  
Maximum Deviation ◽  
Improve Performance ◽  
Central Section ◽  
Mixing Chamber ◽  
Two Sides

In order to study the effect of complementary pulp distribution, computational fluid dynamic (CFD) was used to research on flow characteristic of hydraulic headbox based on complementary pulp distribution. Mass flow rate out of mixing chamber and velocity distribution at slice of headbox were experimented. The results show that because of simplified design, there was a little gradient of velocity and pressure which caused non uniform distribution of mass flow rate out of branch pipes. Distribution of mass flow rate was ascended from inlet of header to outlet and the deviation was - 2.33% and 1.82%. There was intense interference between the jets of branch pipes in mixing chamber and the jets could be sufficiently and complementarily mixed in rows and ranks. But the interference in the jets caused the accumulation of the jets in the central section of mixing chamber and mass flow rate out of mixing chamber in the center was higher than the two sides, and the maximum deviation was 0.538%. Distribution of velocity of pulp stock at slice of headbox was very gentle and curve of distribution presented only slight fluctuation. The maximum deviation of velocity was only 0.175%. From the results of the experiment, the test values of mass flow rate out of mixing chamber were inosculated with the calculated values and tested values of velocity at the slice of headbox were in accordance with the calculated values. The results of experiment explained that the method of complementary pulp distribution was reasonable and could obviously improve performance of pulp distribution of hydraulic headbox.

PV/T Performance Evaluation as Electricity Generation and Hot Air Supplier for Fully and Partially Covered with PV Modules

2020 ◽  
Vol 38 (7A) ◽  
pp. 1001-1015
Author(s):  
Jalal M. Jalil ◽  
Ahmed A. Hussein ◽  
Anwar J. Faisal
Keyword(s):  
Mass Flow Rate ◽  
Air Temperature ◽  
Mass Flow ◽  
Flow Rate ◽  
Fluid Dynamic ◽  
Electrical Power ◽  
Energy System ◽  
Solar Simulator ◽  
Pv Modules ◽  
T System

The solar energy system is environmentally friendly and the utilization of photovoltaic thermal collectors, (PV/T) has attracted more attention, which directly converts solar radiation into electricity and thermal energy simultaneously. This study investigated the air biased Photovoltaic thermal hybrid solar collectors, (PV/T) trend for two cases, denominate case one (PV/T system fully covered with PV modules), and case tow (PV/T system partially covered with glass). The studied parameters were solar irradiance and the air mass flow rate. The investigation has been performed in terms of outlet air temperature, electrical power, thermal and electrical efficiencies. A numerical model was developed using the computational fluid dynamic program (CFD) and the results were compared with the experimental measurements that carried out from indoor conditions using a solar simulator. A good agreement has been achieved between experimental and numerical results. The performance of both cases one and case two concluded that the PV/T system should be operating at a moderate air flow rate of 0.013 kg/s, which is the best mass flow rate. In addition, it has been observed that for case tow the maximum outlet air temperature and electric powers were 44.3 oC and 26.6 W, respectively. For case one, thermal and electrical efficiencies were found 34% and 10%, respectively, based on the experimental data, while for case 2, the maximum thermal and electrical efficiencies were found to be 48.9 and 9.1%, respectively.

A CFD Analysis of Flow Blockage Phenomena in ALFRED LFR DEMO Fuel Assembly

2014 ◽  
Author(s):  
I. Di Piazza ◽  
M. Tarantino ◽  
F. Magugliani ◽  
A. Alemberti
Keyword(s):  
Active Region ◽  
Fuel Assembly ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Fluid Dynamic ◽  
Critical Conditions ◽  
Recirculation Region ◽  
Temperature Peak ◽  
Flow Blockage

A CFD study has been carried out on fluid flow and heat transfer in the HLM-cooled Fuel Pin Bundle of the ALFRED LFR DEMO. In the context of GEN-IV Heavy Liquid Metal-cooled reactors safety studies, the flow blockage in a Fuel sub-assembly is considered one of the main issues to be addressed and the most important and realistic accident for LFR Fuel Assembly. The present paper is a first step towards a detailed analysis of such phenomena, and a CFD model and approach is presented to have a detailed thermo-fluid dynamic picture in the case of blockage. The closed hexagonal, grid-spaced fuel assembly of the LFR ALFRED has been modeled and computed. At this stage, the details of the spacer grids have not been included, but a conservative analysis has been carried out based on the current main geometrical and physical features. Reactivity feedback, as well as axial power profile, have not been included in this analysis. Results indicate that critical conditions, with clad temperatures around ∼900°C, are reached with blockage larger than 30% in terms of area fraction. Two main effects can be distinguished: a local effect in the wake/recirculation region downstream the blockage and a global effect due to the lower mass flow rate in the blocked subchannels; the former effect gives rise to a temperature peak behind the blockage and it is dominant for large blockages (>20%), while the latter effect determines a temperature peak at the end of the active region and it is dominant for small blockages (<10%). The blockage area has been placed at the beginning of the active region, so that both over-mentioned phenomena can fully take place. The mass flow rate at the different degree of blockage has been imposed from preliminary system code simulations. Transient analyses with fully resolved SST-ω turbulence model have been carried out and results indicate that a blockage of ∼15% (in terms of blocked area) leads to a maximum clad temperature around 800 °C, and this condition is reached in a characteristic time of 3–4 s without overshoot. Local clad temperatures around 1000 °C can be reached for blockages of 30% or more. CFD simulations indicate that Blockages >15% could be detected by putting some thermocouples in the plenum region of the FA.

scholarly journals Use of CFD for Analysis of HYDRAM- An Approach

2021 ◽  
Vol 9 (VII) ◽  
pp. 334-337
Author(s):  
Ajay B. Mahajan
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Systematic Study ◽  
Computational Fluid Dynamic ◽  
Fluid Dynamic ◽  
Water Discharge ◽  
Pump Performance

This paper presents the analysis of the existing hydraulic ram pump performance using computational fluid dynamic (CFD). The study specifies that mass flow rate at inlet and outlet on CFD. These are based on a systematic study of hydraulic ram pump and testing of on hydraulic ramp pump model. For which we consider literatures reviews & some of them are used for the analysis. CFD approach is used in this paper for estimating the water discharge.

scholarly journals Pressure Pulsation and Cavitation Phenomena in a Micro-ORC System

Energies ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 2186 ◽  
Author(s):  
Nicola Casari ◽  
Ettore Fadiga ◽  
Michele Pinelli ◽  
Saverio Randi ◽  
Alessio Suman
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Fluid Dynamic ◽  
Pressure Rise ◽  
Inlet Section ◽  
Gear Pump ◽  
Pump Operation ◽  
Transient Phenomena ◽  
Pumping System

Micro-ORC systems are usually equipped with positive displacement machines such as expanders and pumps. The pumping system has to guarantee the mass flow rate and allows a pressure rise from the condensation to the evaporation pressure values. In addition, the pumping system supplies the organic fluid, characterized by pressure and temperature very close to the saturation. In this work, a CFD approach is developed to analyze from a novel point of view the behavior of the pumping system of a regenerative lab-scale micro-ORC system. In fact, starting from the liquid receiver, the entire flow path, up to the inlet section of the evaporator, has been numerically simulated (including the Coriolis flow meter installed between the receiver and the gear pump). A fluid dynamic analysis has been carried out by means of a transient simulation with a mesh morphing strategy in order to analyze the transient phenomena and the effects of pump operation. The analysis has shown how the accuracy of the mass flow rate measurement could be affected by the pump operation being installed in the same circuit branch. In addition, the results have shown how the cavitation phenomenon affects the pump and the ORC system operation compared to control system actions.

Control of Deep-Hysteresis Aeroengine Compressors1

1996 ◽  
Vol 122 (1) ◽  
pp. 140-152 ◽  
Author(s):  
Hsin-Hsiung Wang ◽  
Miroslav Krstic´ ◽  
Michael Larsen
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Fluid Dynamic ◽  
Convex Combination ◽  
Pressure Rise ◽  
Open Loop ◽  
Rotating Stall ◽  
Qualitative Description ◽  
Entire Family

Frequencies of higher-order modes of fluid dynamic phenomena participating in aeroengine compressor instabilities far exceed the bandwidth of available (affordable) actuators. For this reason, most of the heretofore experimentally validated control designs for aeroengine compressors have been via low-order models—specifically, via the famous Moore-Greitzer cubic model (MG3). While MG3 provides a good qualitative description of open-loop dynamic behavior, it does not capture the main difficulties for control design. In particular, it fails to exhibit the so-called “right-skew” property which distinguishes the deep hysteresis observed on high-performance axial compressors from a small hysteresis present in the MG3 model. In this paper we study fundamental feedback control problems associated with deep-hysteresis compressors. We first derive a parametrization of the MG3 model which exhibits the right skew property. Our approach is based on representing the compressor characteristic as a convex combination of a usual cubic polynomial and a nonpolynomial term carefully chosen so that an entire family of right-skew compressors can be spanned using a single parameter ε. Then we develop a family of controllers which are applicable not only to the particular parametrization, but to general Moore-Greitzer type models with arbitrary compressor characteristics. For each of our controllers we show that it achieves a supercritical (soft) bifurcation, that is, instead of an abrupt drop into rotating stall, it guarantees a gentle descent with a small stall amplitude. Two of the controllers have novel, simple, sensing requirements: one employs only the measurement of pressure rise and rotating stall amplitude, while the other uses only pressure rise and the mass flow rate (1D sensing). Some of the controllers which show excellent results for the MG3 model fail on the deep-hysteresis compressor model, thus justifying our focus on deep-hysteresis compressors. Our results also confirm experimentally observed difficulties for control of compressors that have a high value of Greitzer’s B parameter. We address another key issue for control of rotating stall and surge—the limited actuator bandwidth—which is critical because even the fastest control valves are often too slow compared to the rates of compressor instabilities. Our conditions show an interesting trade-off: as the actuator bandwidth decreases, the sensing requirements become more demanding. Finally, we go on to disprove a general conjecture in the compressor control community that the feedback of mass flow rate, known to be beneficial for shallow-hysteresis compressors, is also beneficial for deep-hysteresis compressors. [S0022-0434(00)03101-4]

Flow Characteristic and Optimal Design of Rectangularly Tapered Header Based on CFD

2014 ◽  
Vol 552 ◽  
pp. 20-23
Author(s):  
Xiao Hui Ji ◽  
Wei Liu
Keyword(s):  
Pressure Distribution ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Fluid Dynamic ◽  
Branch Pipe ◽  
Expected Value ◽  
Pressure Curve ◽  
Horizontal Line ◽  
Remarkable Deviation

In order to study reasonable structure of rectangular tapered header, the methed of computatation fluid dynamic was used to research pulp distribution characteristic of the rectangularly tapered pulp distributor and to optimize its structure. The results show that velocity distribution and pressure distribution in the tapered header were not uniform and the mass flow rate out of branch pipes was obviously accrescent from inlet of header to outlet of header. There was remarkable deviation comparison to expected value of mass flow rate. The real backwall shape of the rectangularly tapered head was a complicated curve that was obviously different to the simplified header at area of the inlet and the outlet. The pressure distribution in the optimally designed header was more uniform and the pressure curve at the location corresponding to branch pipes was nearly a horizontal line. The mass flow rate distribution out of the branch pipes was more uniform else and was close to the expected value curve. The deviation of the mass flow rate in every branch pipe was less than 1%.

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