scholarly journals Analysis of effective pore pressure in asphalt pavement based on computational fluid dynamics calculation

2017 ◽  
Vol 9 (2) ◽  
pp. 168781401668522 ◽  
Author(s):  
Xuedong Guo ◽  
Mingzhi Sun ◽  
Wenting Dai
Keyword(s):  
Fluid Dynamics ◽  
Asphalt Pavement ◽  
Micromechanical Model ◽  
Lower Boundary ◽  
Pore Wall ◽  
Maximum Pressure ◽  
Vehicle Speed ◽  
Exit Slit ◽  
Traffic Loading ◽  
Dynamics Calculation

A micromechanical model was established based on the fluid dynamics theory. This model could be used to calculate several kinds of data when the asphalt pavement under the influence of traffic loading is in water-saturated condition. The results showed that the maximum pressure inside the effective pore was located at the junction between exit slits and the pore wall. There was a positive correlation between the pressure and the vehicle speed. Therefore, the repeated traffic loading could cause emulsification, shift and even peeling of the asphalt membrane. Moreover, the bigger size of the exit slit is, the higher velocity of the fluid has. The high velocity flow keeps scouring both the exit slit and the lower boundary of pore wall. It will cause a bigger slit. Pressure distribution inside the effective pore is related to the number of the exit slit which connect with the pore. More exit slits means bigger pressure inside the effective pore. In addition, if asphalt membranes at exit slits have micro-cracking, the cumulative damage could appear easily and asphalt membranes could be peeled easily. Finally, a test was conducted so as to obtain the bonding strength and adhesion strength between asphalt and aggregate. Then, we can get accurate damage form and position during the scour process by comparing the numerical simulation results with experiment results.

Study on Load Stress of Lean Concrete Base in Asphalt Pavement

2012 ◽  
Vol 178-181 ◽  
pp. 1495-1498
Author(s):  
Li Jun Suo
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Asphalt Pavement ◽  
Element Model ◽  
Pavement Design ◽  
The Other ◽  
Three Dimension ◽  
Traffic Loading ◽  
Concrete Base

Load stress, which is caused by traffic loading, is important parameter used in the analysis of the new pavement design. In order to study the load stress of lean concrete base in the asphalt pavement, first of all, three–dimension finite element model of the asphalt pavement is established. The main objectives of the paper are investigated. One is calculation for load stress of lean concrete base, and the other is analysis for relationship between load stress of lean concrete base and parameters, such as thickness, modulus. The results show that load stress of lean concrete base decreases, decreases and increases with increase of base’s thickness, surface’s thickness and ratio of base’s modulus to foundation’s modulus respectively. So far as the traffic axle loading is concerned, it has a significant impact on load stress of lean concrete base, and it can be seen from results that when load is taken from 100kN to 220kN, load stress increases quickly with the increase of the traffic axle loading.

Design and Optimization of the Restrictor of a Race Car

2015 ◽  
Author(s):  
Prithvi Raj Kokkula ◽  
Shashank Bhojappa ◽  
Selin Arslan ◽  
Badih A. Jawad
Keyword(s):  
Fluid Dynamics ◽  
Pressure Drop ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Air Flow ◽  
Intake Manifold ◽  
Maximum Pressure ◽  
Cross Sectional ◽  
Formula Sae

Formula SAE is a student competition organized by SAE International. The team of students design, manufacture and race a car. Restrictions are imposed by the Formula SAE rules committee to restrict the air flow into the intake manifold by putting a single restrictor of 20 mm. This rule limits the maximum engine power by reducing the mass flow rate flowing to the engine. The pull is greater at higher rpms and the pressure created inside the cylinder is low. As the diameter of the flow path is reduced, the cross sectional area for flow reduces. For cars running at low rpm when the engine requires less air, the reduction in area is compensated by accelerated flow of air through the restrictor. Since this is for racing purpose cars here are designed to run at very high rpms where the flow at the throat section reach sonic velocities. Due to these restrictions the teams are challenged to come up with improved restrictor designs that allow maximum pressure drop across the restrictor’s inlet and outlet. The design considered for optimizing a flow restrictor is a venturi type having 20 mm restriction between the inlet and the outlet complying with the rules set by Formula SAE committee. The primary objective of this work is to optimize the flow restriction device that achieves maximum mass flow and minimum pull from the engine. This implies the pressure difference created due to the cylinder pressure and the atmospheric pressure at the inlet should be minimum. An optimum flow restrictor is designed by conducting analysis on various converging and diverging angles and coming up with an optimum value. Venturi type is a tubular pipe with varying diameter along its length, through which the fluid flows. Law of governing fluid dynamics states that the “Velocity of the fluid increases as it passes through the constriction to satisfy the principle of continuity”. An equation can be derived from the combination of Bernoulli’s equation and Continuity equation for the pressure drop due to venturi effect. [1]. A Computational Fluid Dynamics (CFD) tool is used to calculate the minimum pressure drop across the restrictor by running a series of analysis on various converging and diverging angles and calculating the pressure drop. As a result, an optimum air flow restrictor is achieved that maximizes the mass flow rate and minimizes the engine pull.

scholarly journals The Influence of the Carbo-Glass Geogrid-Reinforcement on the Fatigue Life of the Asphalt Pavement Structure / Wpływ Zbrojenia Siatka Weglowo–Szklana Na Trwałosc Zmeczeniowa Asfaltowej Nawierzchni Drogowej

2012 ◽  
Vol 58 (1) ◽  
pp. 97-113 ◽  
Author(s):  
J. Górszczyk ◽  
S. Gaca
Keyword(s):  
Fatigue Life ◽  
Asphalt Pavement ◽  
Field Tests ◽  
Traffic Loading ◽  
Geogrid Reinforcement ◽  
Traffic Conditions ◽  
Pavement Structure ◽  
Number Of Cycles ◽  
The One ◽  
Stress Fatigue

Abstract This paper describes the analyses of the fatigue life of the asphalt pavement reinforced with geogrid interlayer under traffic loading. Finite Element ANSYS package with using nCode applications, as well as macros specially designed in APDL programming script and VBA were used to model the considered problem. Our analysis included computation of stress, fatigue life, damage matrix and rainflow matrix. The method applied was the one of fatigue calculation: stress - number of cycles in short S-N. On the basis of the performed high cycle fatigue analysis, the influence of the location of the used geogrid and of its bond with asphalt layers on the fatigue life and the work of the asphalt pavement structure were determined. The study was carried out for three temperature seasons i.e. spring and fall (assumed as one season), winter and summer. The variability of the traffic conditions were taken into account by assuming weekly blocks of traffic loading. The calculations were made using the real values of loading measured in field tests on the German highways by means of HS-WIM weighing system. As a result of the performed tests, it was proved that the use of geogrid-reinforcement may prolong the fatigue life of the asphalt pavement. However, it is required that: the geogrid should be located in the tension zone as low as possible in the structure of the asphalt layers. Moreover, it is necessary to provide high stiffness of the bond between the geogrid and the asphalt layers.

Predicting the Treatment Response of Oral Appliances for Obstructive Sleep Apnea Using Computational Fluid Dynamics and Fluid-Structure Interaction Simulations

2013 ◽  
Author(s):  
Moyin Zhao ◽  
Tracie Barber ◽  
Peter Cistulli ◽  
Kate Sutherland ◽  
Gary Rosengarten
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Obstructive Sleep Apnea ◽  
Sleep Apnea ◽  
Pressure Drop ◽  
Treatment Response ◽  
Fluid Structure Interaction ◽  
Maximum Pressure ◽  
Structure Interaction ◽  
Obstructive Sleep

In this study we used computational fluid dynamics (CFD) to analyze the therapeutic effect of an oral device (mandibular advancement splint – MAS, that protrudes the lower jaw during sleep) as a treatment for Obstructive Sleep Apnea (OSA). Anatomically-accurate upper airway (UA) computational models were reconstructed from magnetic resonance images (MRI) of 7 patients with and without a MAS device fitted. CFD simulations of UA airflow were performed at the maximum flow rate during inspiration. The CFD results indicated the lowest pressure often occurs close to the soft palate and the base of the tongue. The airway pressure gradient was estimated as the best indicator for treatment response since the change in the pressure drop forms a linear correlation with the change in patients’ Apnea-Hypopnea Index (AHI). This correlation has the potential to be developed into a model for predicting the outcome of the MAS treatment. However the rigid wall assumption of CFD models is the major uncertainty. To overcome this uncertainty we set up a full fluid-structure interaction model for a typical responder case with a compliant UA wall. The results demonstrated the different UA flow field associated with using MAS alleviated the airway collapse, which was successfully predicted for the untreated patient. We thus show for the first time that FSI is more accurate than CFD with rigid walls for the study of OSA, and can predict treatment response. Comparison of the FSI and CFD results for the UA flow and pressure profiles showed variation between the models. The structural deflection in oropharynx effectively reformed the flow pattern, however, the maximum pressure drops of both results were close. This supports the competence of the CFD method in clinical applications, where maximum pressure drop data can be used to develop a treatment-predicting model.

A SEARCH OF AN INDUCER GEOMETRY THAT IS BENEFICIAL FOR LIFTING PARAMETERS OF A LIFTED OBJECT OF A SELECTED SHAPE

Tribologia ◽  
2019 ◽  
Vol 287 (5) ◽  
pp. 13-17
Author(s):  
Bartosz BASTIAN ◽  
Rafał GAWARKIEWICZ
Keyword(s):  
Fluid Dynamics ◽  
Experimental Verification ◽  
Vibration Characteristics ◽  
Squeeze Film ◽  
Acoustic Levitation ◽  
Dynamics Calculation ◽  
Dimension Ratio

The literature describes acoustic levitation phenomena with the utilization of air squeeze film between the vibrating inducer and the lifted object. The objective of the study is to determine the shape of the inducer with vibration characteristics that would allow the levitation of an object of the assumed geometry. In this paper, the influence of the dimension ratio of the inducer on the frequency of the first mode of vibration was presented. CFD calculations for a selected dimension series were performed with the goal of the determination of lifting conditions. The data obtained from the analysis will be used to manufacture an inducer that will serve as an experimental verification for the fluid dynamics calculation.

A Practical Method to Study Over and Under-Pressurizing of Ship Tanks During Ballasting and Deballasting

2008 ◽  
Author(s):  
Manoj Kumar
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Parametric Study ◽  
Pressure Rise ◽  
Practical Method ◽  
Hole Diameter ◽  
Maximum Pressure ◽  
Opening And Closing ◽  
Hull Damage

There have been many incidents of hull damage due to over and under-pressurizing of ship tanks during ballasting and deballasting. A safety relief hole of 6 to 8mm diameter is generally provided in Air-pipes to prevent accidental over and under-pressurizing of ship tanks during ballasting and deballasting. This paper investigates the pressure rise and drop inside the tank assuming the air-pipe to be closed. A practical method based on Computational Fluid Dynamics has been presented to find out the maximum pressure rise or drop. A parametric study, based on varying relief hole diameter, has been carried out. The investigation brings to prospective the extent of pressure rise or drop, and hence the damages that can occur due to poor operation of the Air-pipes during ballasting and deballasting and a need for automated opening and closing of the Air-pipes for a safer ship.

Effect of Rubber Hardness and Tire Size on Tire-Pavement Interaction Noise

2019 ◽  
Vol 47 (4) ◽  
pp. 258-279 ◽  
Author(s):  
Tan Li ◽  
Ricardo Burdisso ◽  
Corina Sandu
Keyword(s):  
Asphalt Pavement ◽  
Sound Intensity ◽  
Leading Edge ◽  
Noise Spectrum ◽  
Vehicle Speed ◽  
Passenger Cars ◽  
Tire Noise ◽  
Order Tracking ◽  
Pattern Noise ◽  
Noise Data

ABSTRACT Tire-pavement interaction noise (TPIN) is a dominant noise source for passenger cars and trucks above 25 mph (40 km/h) and above 43 mph (70 km/h), respectively. TPIN is generated due to excitations of the tread pattern and pavement texture. For the same tread pattern and pavement texture at the same speed, TPIN might also be influenced by the tire structure (e.g., the tread rubber hardness and tire size). In the present study, 42 tires with different rubber hardnesses and/or tire sizes were tested at five different speeds (45–65 mph, i.e., 72–105 km/h) on a nonporous asphalt pavement (a section of U.S. Route 460, both eastbound and westbound). An on-board sound intensity system was instrumented on the test vehicle to collect the tire noise data at both the leading edge and the trailing edge of the contact patch. An optical sensor recording the once-per-revolution signal was also installed to monitor the vehicle speed and, more importantly, to provide the data needed to perform the order-tracking analysis to break down the tire noise into two components. These two components are the tread pattern noise and the non–tread pattern noise. It is concluded that for the nonporous asphalt pavement tested, the non–tread pattern noise increases with rubber hardness by ∼0.23 dBA/Shore A. The tire carcass width (section width plus two times section height) influences the central frequencies of the non–tread pattern noise spectrum; the central frequencies decrease as the tire carcass width increases.

scholarly journals Revisiting the Simplified Bernoulli Equation

2010 ◽  
Vol 4 (1) ◽  
pp. 123-128 ◽  
Author(s):  
Jeffrey J Heys ◽  
Nicole Holyoak ◽  
Anna M Calleja ◽  
Marek Belohlavek ◽  
Hari P Chaliki
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Stokes Equations ◽  
Dynamics Simulation ◽  
Maximum Pressure ◽  
Bernoulli Equation ◽  
Computational Fluid Dynamics Simulation ◽  
Valvular Stenosis ◽  
Significant Difference

Background: The assessment of the severity of aortic valve stenosis is done by either invasive catheterization or non-invasive Doppler Echocardiography in conjunction with the simplified Bernoulli equation. The catheter measurement is generally considered more accurate, but the procedure is also more likely to have dangerous complications. Objective: The focus here is on examining computational fluid dynamics as an alternative method for analyzing the echo data and determining whether it can provide results similar to the catheter measurement. Methods: An in vitro heart model with a rigid orifice is used as a first step in comparing echocardiographic data, which uses the simplified Bernoulli equation, catheterization, and echocardiographic data, which uses computational fluid dynamics (i.e., the Navier-Stokes equations). Results: For a 0.93cm2 orifice, the maximum pressure gradient predicted by either the simplified Bernoulli equation or computational fluid dynamics was not significantly different from the experimental catheter measurement (p > 0.01). For a smaller 0.52cm2 orifice, there was a small but significant difference (p < 0.01) between the simplified Bernoulli equation and the computational fluid dynamics simulation, with the computational fluid dynamics simulation giving better agreement with experimental data for some turbulence models. Conclusion: For this simplified, in vitro system, the use of computational fluid dynamics provides an improvement over the simplified Bernoulli equation with the biggest improvement being seen at higher valvular stenosis levels.

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