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This research presents a numerical investigation of the flow field and heat transfer of a Viscoplastic fluid, The Bingham-Papanastasiou model is used to examine the flow field and forced convection heat transfer of a Viscoplastic fluid between two concentric cylinders with a wavy inner surface. By focusing on this particular configuration (wavy inner cylinder shape), where the inner surface exhibits as the hot wall while the outer surface is considered as the cold wall. This investigation is numerically achieved by using the Comsol Multiphysics, which is based on the finite-volume method, employing Galerkin's method for solving the governing equations. The parameters studied in this research are expressed with the following values: r/R=1/3, Reynolds number (Re=1, 10, 50), and undulation number (nu=0, 6, 12, 24). Increasing the inertia parameter results in a higher intensity of thermal buoyancy, positively influencing heat transfer, particularly at Re=50. Furthermore, the acceleration of flow within the investigated space improves the hydrodynamic behavior, facilitating the exchange of thermal energy between the hot and cold walls. Additionally, it has been discovered that an undulating shape with a specific number of undulations (nu=6) maximizes hydrothermal performance within the investigated volume. The presence of these undulations enhances fluid mixing and disrupts the formation of stagnant regions, which leading to improved heat transfer. [ABSTRACT FROM AUTHOR]

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In the United States, the Superpave Asphalt Binder Performance Grading (PG) system proposed by the Strategic Highway Research Program (SHRP) is the most common method used to characterize the performance-related properties of unmodified and polymer-modified asphalt binders. Dynamic shear modulus (G*) and phase angle (δ) are the two main binder properties and they are measured using a dynamic shear rheometer (DSR) with parallel plate geometry and either a 1-mm or 2-mm gap between the plates. Since these Superpave parameters were developed for binders that do not contain additives or particulates, the California Department of Transportation (Caltrans) does not use them for asphalt rubber binder specifications. Instead, penetration and viscosity are used as acceptance of quality control; however, these parameters do not necessarily provide a satisfactory link between the measured binder properties and potential performance in the field over a range of operating temperatures. In California, current specifications require that crumb rubber particles used to produce asphalt rubber binder in the “wet process” must be smaller than 2.36 mm (i.e., 100 percent passing the #8 sieve), and typically these particles vary in size between 1 mm and 2 mm. Consequently, when the parallel plate geometry is used to test this type of binder, the larger incompletely digested rubber particles can contact the plates. If this occurs, the rubber particle rheology can potentially dominate the results, which in turn may not be representative of the modified binder as a whole. To address this problem, a potentially more appropriate DSR testing protocol using concentric cylinder geometry was investigated in Phase 1 of this study to explore an alternative means of determining the performance properties of asphalt rubber binders. Phase 2 of the study, documented in this report, continued the investigation into the use of the concentric cylinder geometry and alternate parallel plate geometry with a 3-mm gap. The use of these geometries for intermediate-temperature testing and multiple stress creep recovery testing was also investigated, along with modified procedures for short- and long-term aging in the rolling thin-film oven and pressurized aging vessel, respectively, and specimen preparation procedures for bending beam rheometer (BBR) testing. Limited mix testing was also conducted to relate high- and low-temperature mix performance to the performance grades determined for the binders used in the mixes. The concentric cylinder testing approach to measuring the rheological properties of asphalt rubber binders is considered feasible, and that with its use, the edge effects and trimming issues associated with parallel plate testing can be eliminated. However, the concentric cylinder method requires a longer testing time and a larger binder sample than the parallel plate test method. Initial findings from performance grading and related mix testing indicate that the incompletely digested rubber particles, which have different sensitivities to temperature and applied stress and strain than the asphalt binder, appear to dominate the test results. This will need to be factored into analyses and interpretation of rheology and mix performance test results. The proposed modifications to the short- and long-term aging procedures and to the BBR specimen preparation procedures are considered to be more aligned with the original intent of the tests and will likely reduce the variability between replicate specimens during testing. The results from Phase 2 support the continuation of testing, which should be in line with the original workplan and objectives of this research effort. The research should continue to refine the testing procedures on additional field binder sources, assess the repeatability and reproducibility of any proposed test methods, and evaluate the applicability of the results to the actual performance properties of mixes produced with asphalt rubber binders.

In this article homogeneous-heterogeneous (HH) reactions within MHD mixed convection flow on viscous fluid having the characteristic of heat generation/absorption between infinitely long concentric cylinders have been examined. Momentum and energy equations in dimensionless form have been converted into Bessel's differential equations for heat generation/absorption cases respectively, these equations are solved analytically. Furthermore, Runge-Kutta (R–K) technique has been applied for the nonlinear ODE of the concentration profile. Velocity, temperature and concentration profiles have been elaborated graphically by utilizing the impact of physical parameters Kn,H,Gr/Re,M,K1,K2andSc. The mixed convection parameter upsurges the velocity on the heated (inner) cylinder, and it decreases on the cold (outer) cylinder. Temperature declines through Rd when heat is generated, and it rises when heat is absorbed on the heated (inner) cylinder and a reverse impact is found on the cold (outer) cylinder. The concentration profile falls away for escalating values of Schmidt number Sc and homogeneous reaction parameter K1.

In the United States, the Superpave Asphalt Binder Performance Grading (PG) system proposed by the Strategic Highway Research Program (SHRP) is the most common method used to characterize the performance-related properties of unmodified and polymer-modified asphalt binders. Dynamic shear modulus (G*) and phase angle (δ) are the two main binder properties and they are measured using a dynamic shear rheometer (DSR) with parallel plate geometry and either a 1-mm or 2-mm gap between the plates. Since these Superpave parameters were developed for binders that do not contain additives or particulates, the California Department of Transportation (Caltrans) does not use them for asphalt rubber binder specifications. Instead, penetration and viscosity are used as acceptance of quality control; however, these parameters do not necessarily provide a satisfactory link between the measured binder properties and potential performance in the field over a range of operating temperatures. In California, current specifications require that crumb rubber particles used to produce asphalt rubber binder in the “wet process” must be smaller than 2.36 mm (i.e., 100 percent passing the #8 sieve), and typically these particles vary in size between 1 mm and 2 mm. Consequently, when the parallel plate geometry is used to test this type of binder, the larger incompletely digested rubber particles can contact the plates. If this occurs, the rubber particle rheology can potentially dominate the results, which in turn may not be representative of the modified binder as a whole. To address this problem, a potentially more appropriate DSR testing protocol using concentric cylinder geometry was investigated in Phase 1 of this study to explore an alternative means of determining the performance properties of asphalt rubber binders. Phase 2 of the study, documented in this report, continued the investigation into the use of the concentric cylinder geometry and alternate parallel plate geometry with a 3-mm gap. The use of these geometries for intermediate-temperature testing and multiple stress creep recovery testing was also investigated, along with modified procedures for short- and long-term aging in the rolling thin-film oven and pressurized aging vessel, respectively, and specimen preparation procedures for bending beam rheometer (BBR) testing. Limited mix testing was also conducted to relate high- and low-temperature mix performance to the performance grades determined for the binders used in the mixes. The concentric cylinder testing approach to measuring the rheological properties of asphalt rubber binders is considered feasible, and that with its use, the edge effects and trimming issues associated with parallel plate testing can be eliminated. However, the concentric cylinder method requires a longer testing time and a larger binder sample than the parallel plate test method. Initial findings from performance grading and related mix testing indicate that the incompletely digested rubber particles, which have different sensitivities to temperature and applied stress and strain than the asphalt binder, appear to dominate the test results. This will need to be factored into analyses and interpretation of rheology and mix performance test results. The proposed modifications to the short- and long-term aging procedures and to the BBR specimen preparation procedures are considered to be more aligned with the original intent of the tests and will likely reduce the variability between replicate specimens during testing. The results from Phase 2 support the continuation of testing, which should be in line with the original workplan and objectives of this research effort. The research should continue to refine the testing procedures on additional field binder sources, assess the repeatability and reproducibility of any proposed test methods, and evaluate the applicability of the results to the actual performance properties of mixes produced with asphalt rubber binders.

The recently proposed short back extrusion (SBE) method is an improved immersed-type BE method. A translational concentric cylinder rheometer is used. As the measurement position is inside the sample, the upflow in the annular space is smooth even over a short distance (5 to 15 mm). Measurement over a short distance decreases the amount of sample adhering to the plunger; this facilitates repeated measurements, as the removal of the adhering sample after each measurement is not needed. The rheometer analysis program can perform automated Newtonian, power-law, and Herschel–Bulkley flow analyses by introducing novel mathematical solutions and obtaining constitutive equations for the various flow types. Herschel–Bulkley fluids exhibit semisolid properties and thixotropic flow characteristics, specifically, stress growth or time-dependent behavior. Currently, SBE viscometry is the only available method to evaluate viscosity and yield stress simply and simultaneously and this study presented the results compared with rotational cone-plate viscometry. [ABSTRACT FROM AUTHOR]

Porous media insert is a simple technique to enhance heat transfer, which has been used in different applications. This useful passive improvement technique could be applied on the rotating/fixed inner/outer wall of a/an concentric/eccentric cylinder to improve heat transfer. This configuration has extensive applications in different fields, especially in the bearing technology. In the current study, a numerical research has been done to explore the effect of inserting a porous layer on the inner rotating wall of an eccentric cylinder on the heat transfer. The effects of different parameters including Richardson number, Rayleigh number, Darcy number, the eccentricity, and the inner wall peripheral location are investigated. The results show that using porous media with higher Darcy numbers enhances more heat transfer (for example, about 70% at Da = 10−3 with respect to 30% at Da = 10−6). Also, porous media insert improves heat transfer by about 90% in the medium Richardson numbers (Ri = 0.1). The results show that the effect of porous media insert becomes very considerable as the Rayleigh number increases. For example, porous media insert could augment heat transfer by three times at Ra = 9 × 104. [ABSTRACT FROM AUTHOR]

The back extrusion (BE) method is a well‐known translational concentric cylinder viscometry that can analyze viscosity from the force–time curve of a cylindrical plunger pushed into a cylindrical cup filled with a sample fluid. It can analyze Newtonian, power‐law, and Herschel–Bulkley flows. However, the plunger must be moved 100 mm or more from the sample surface toward the cup bottom, any sample fluid adhering to the plunger must be removed. Moreover, given the complexity of the calculation steps, the BE method is not as widely. The short back extrusion (SBE) method proposed in this study is an improved immersed‐type BE method. By setting the measurement position inside the sample, the upflow in the annular space is smooth even over a short distance (5–15 mm). Measurement over a short distance decreases the amount of sample adhered to the plunger, mitigating the need to remove any sample from the plunger after each measurement, thereby facilitating repeated measurements. A program automatically determines flow type and, using novel mathematical formulas, it calculates the measured characteristics of the flow. In addition, the greatest advantage of the SBE method is that it can measure samples containing solids. It can be measured in a state in which a person usually eats, because the larger the stress required for the flow, the wider the gap. Moreover, its measurement accuracy is comparable to cone‐plate analysis, and the linear region of the analysis area is wide with less destructive movement. [ABSTRACT FROM AUTHOR]

Transport properties of natural silicate melts at super-liquidus temperatures are reasonably well understood. However, migration and transport of silicate melts in the Earth’s crust and at its surface generally occur at sub-liquidus temperatures and in settings where the melts undergo crystallization under various cooling and/or decompression conditions. In such dynamic situations the occurrence of processes such as the release of latent heat during phase changes, viscous heating, thermal advection and -inertia, and changing heat capacity, all represent potential influences on the state, and thereby on the physico-chemical behavior of the system. To date, rheological data at sub-liquidus temperatures are scarce and cooling-rate dependent, disequilibrium rheological data are virtually absent. In fact, no in situ thermal characterization of liquid or multiphase mixtures during rheological experiments, under either static or dynamic thermal conditions has been presented to date. Here we describe a new experimental setup for in situ thermal characterization of cooling/crystallizing lavas during viscosity measurement at temperatures up to 1600 °C. We use this device to recover in situ , real-time, observations of the combined rheological and thermal evolution of natural, re-melted lava samples during the transient disequilibrium conditions characteristic of lava flows and shallow crustal magma migration and storage systems in nature. We present the calibration procedure and the method employed to recover the thermal evolution of an experimental sample during flow in varying shear regimes, assess the experimental uncertainty and show the ability of the apparatus to measure the release of latent heat of crystallization during transient rheological experiments. We further report the results from a first experimental study on the rheological and thermal evolution of a basaltic lava undergoing continuous cooling at a series of different cooling rates and discuss the implications of the results for magma migration and lava flow emplacement. [ABSTRACT FROM AUTHOR]