The Experts below are selected from a list of 288 Experts worldwide ranked by ideXlab platform
J.g. Cordey - One of the best experts on this subject based on the ideXlab platform.
-
application of Dimensionless Parameter scaling techniques to the design and interpretation of magnetic fusion experiments
Plasma Physics and Controlled Fusion, 2008Co-Authors: T.c. Luce, C.c. Petty, J.g. CordeyAbstract:A review of the application of Dimensionless Parameter scaling techniques to magnetic fusion experiments is presented. Because the methods of this type of analysis are not generally known, a detailed discussion of the basis for these techniques is given, including examples. The primary applications and successes of these methods in magnetic fusion research are in the area of transport of energy and particles across surfaces of constant magnetic flux. The experimental justification for the use of these techniques to describe transport is given, and the applications are reviewed. The two key applications of these techniques, the identification of the underlying physical mechanisms that cause transport and the projection of the transport in future devices from present-day experiments, are extensively discussed. Comparison of the results of Dimensionless Parameter scaling experiments with the regression analysis of multi-machine databases points to limitations in the databases and the analysis of them as the source of the discrepancies. These discrepancies have significant implications for the design optimization of tokamaks, which are discussed here. Finally, the application of Dimensionless Parameter scaling techniques to plasma stability, to the boundary region between closed and open field lines and to divertor operation in the open field line region are reviewed and discussed.
-
Experimental constraints on transport from Dimensionless Parameter scaling studies
Physics of Plasmas, 1998Co-Authors: C.c. Petty, J.g. Cordey, T.c. Luce, D.r. Baker, B. Ballet, T. N. Carlstrom, J.c. Deboo, P. Gohil, R.j. Groebner, B. W. RiceAbstract:The scalings of heat transport with safety factor (q), normalized collisionality (v), plasma beta ({beta}), and relative gyroradius ({rho}*) have been measured on the DIII-D tokamak. The measured {rho}* {beta} and v scalings of heat transport indicate that E x B transport from drive wave turbulence is a plausible basis for anomalous transport. For high confinement (H) mode plasmas where the safety factor was varied at fixed magnetic shear, the effective (or one-fluid) thermal diffusivity was found to scale like {chi}{sub eff} {proportional_to} q{sup 2.3{+-}0.64}, with the ion and electron fluids having the same q scaling to within the experimental errors except near the plasma edge. The scaling of the thermal confinement time with safety factor was in good agreement with this local transport dependence, {tau}{sub th} {proportional_to} q{sup {minus}2.42{+-}0.31}; however, when the magnetic shear was allowed to vary to keep q{sub 0} fixed during the (edge) safety factor scan, a weaker global dependence was observed, {tau}{sub th} {proportional_to} q{sub 95}{sup {minus}1.43{+-}0.23}. This weaker dependence was mainly due to the change in the local value of q between the two types of scans. The combined {rho}*, {beta}, v and q scalings of heat transport for H-mode plasmas on DIII-D reproduce the empirical confinement scaling using physical (Dimensionless) Parameters with the exception of weaker power degradation.
-
A review of the Dimensionless Parameter scaling studies
Plasma Physics and Controlled Fusion, 1996Co-Authors: J.g. Cordey, B. Balet, David Campbell, C. D. Challis, J.p. Christiansen, C. Gormezano, C.w. Gowers, D.g. Muir, E. Righi, G. SaibeneAbstract:The theoretical basis of the Dimensionless Parameter scaling technique is derived and the limitations in its application are discussed. The use of the technique is illustrated by the production on JET of a steady-state ITER similarity pulse having the same and collisionality as the ignited ITER. The key issue of the scaling of the transport with the main Dimensionless Parameter is discussed in detail. Finally, possible shortcomings of the technique are examined.
-
Implications from Dimensionless Parameter scaling experiments
1996Co-Authors: T.c. Luce, B. Balet, C.c. Petty, J.g. CordeyAbstract:The Dimensionless Parameter scaling approach is increasingly useful for predicting future tokamak performance and guiding theoretical models of energy transport. Experiments to determine the {rho}* (gyroradius normalized to plasma size) scaling have been carried out in many regimes. The electron {rho}* scaling is always ``gyro-Bohm``, while the ion {rho}* scaling varied with regime. The ion variation is correlated with both density scale length (L mode, H mode) and current profile. The ion {rho}* scaling in the low-q, H-mode regime is gyro-Bohm, which is the most favorable confinement scaling observed. New experiments in {beta} scaling and collisionality scaling have been carried out in low-q discharges in both L mode and H mode. In L mode, global analysis shows that there is a slightly unfavorable {beta} dependence ({beta}{sup {minus}0.1}) and no {nu}* dependence. In H-mode, global analysis finds a weak {beta} dependence ({beta}{sup 0.1}) and an unfavorable dependence on {nu}*. The lack of significant {beta} scaling spans the range of {beta}{sub N} from 0.25 to 2.0. The very small {beta} dependence in L mode and H mode is in contradiction with the standard global scaling relations. This contradiction in H mode may be indicative of the impact on the H-mode database ofmore » low-n tearing instabilities which are observed at slightly higher {beta}{sub N} in the {beta} scaling experiments. The measured {beta} and {nu}* scalings explain the weak density dependence observed in engineering Parameter scans. It also points to the power of the Dimensionless Parameter approach, since it is possible to obtain a definitive size scaling from experiments on a single tokamak.« less
C.c. Petty - One of the best experts on this subject based on the ideXlab platform.
-
application of Dimensionless Parameter scaling techniques to the design and interpretation of magnetic fusion experiments
Plasma Physics and Controlled Fusion, 2008Co-Authors: T.c. Luce, C.c. Petty, J.g. CordeyAbstract:A review of the application of Dimensionless Parameter scaling techniques to magnetic fusion experiments is presented. Because the methods of this type of analysis are not generally known, a detailed discussion of the basis for these techniques is given, including examples. The primary applications and successes of these methods in magnetic fusion research are in the area of transport of energy and particles across surfaces of constant magnetic flux. The experimental justification for the use of these techniques to describe transport is given, and the applications are reviewed. The two key applications of these techniques, the identification of the underlying physical mechanisms that cause transport and the projection of the transport in future devices from present-day experiments, are extensively discussed. Comparison of the results of Dimensionless Parameter scaling experiments with the regression analysis of multi-machine databases points to limitations in the databases and the analysis of them as the source of the discrepancies. These discrepancies have significant implications for the design optimization of tokamaks, which are discussed here. Finally, the application of Dimensionless Parameter scaling techniques to plasma stability, to the boundary region between closed and open field lines and to divertor operation in the open field line region are reviewed and discussed.
-
Dimensionless Parameter Scaling of Transport in DIII-D
Fusion Science and Technology, 2005Co-Authors: C.c. PettyAbstract:A comprehensive series of Dimensionless Parameter scaling experiments has been undertaken in the DIII-D tokamak with the goals of guiding turbulent transport theories and predicting confinement in future devices. These studies have measured the dependences of transport on the relative gyroradius, beta, collisionality, safety factor, cross-section shape, and ratio of ion to electron temperature. The results from these experiments, which are mainly in favor of drift wave turbulent transport, point to a favorable path for increasing the fusion performance in burning plasma devices.
-
Experimental constraints on transport from Dimensionless Parameter scaling studies
Physics of Plasmas, 1998Co-Authors: C.c. Petty, J.g. Cordey, T.c. Luce, D.r. Baker, B. Ballet, T. N. Carlstrom, J.c. Deboo, P. Gohil, R.j. Groebner, B. W. RiceAbstract:The scalings of heat transport with safety factor (q), normalized collisionality (v), plasma beta ({beta}), and relative gyroradius ({rho}*) have been measured on the DIII-D tokamak. The measured {rho}* {beta} and v scalings of heat transport indicate that E x B transport from drive wave turbulence is a plausible basis for anomalous transport. For high confinement (H) mode plasmas where the safety factor was varied at fixed magnetic shear, the effective (or one-fluid) thermal diffusivity was found to scale like {chi}{sub eff} {proportional_to} q{sup 2.3{+-}0.64}, with the ion and electron fluids having the same q scaling to within the experimental errors except near the plasma edge. The scaling of the thermal confinement time with safety factor was in good agreement with this local transport dependence, {tau}{sub th} {proportional_to} q{sup {minus}2.42{+-}0.31}; however, when the magnetic shear was allowed to vary to keep q{sub 0} fixed during the (edge) safety factor scan, a weaker global dependence was observed, {tau}{sub th} {proportional_to} q{sub 95}{sup {minus}1.43{+-}0.23}. This weaker dependence was mainly due to the change in the local value of q between the two types of scans. The combined {rho}*, {beta}, v and q scalings of heat transport for H-mode plasmas on DIII-D reproduce the empirical confinement scaling using physical (Dimensionless) Parameters with the exception of weaker power degradation.
-
Understanding transport through Dimensionless Parameter scaling experiments
1997Co-Authors: C.c. Petty, T.c. LuceAbstract:The related methods of dimensional analysis, similarity, and scale invariance provide a powerful technique for analyzing physical systems. For example, the complex plasma dynamics governed by the Vlasov-Maxwell system of equations can be characterized by sets of Dimensionless quantities through the application of these techniques. Significant progress has been made recently towards predicting and understanding radial heat transport using Dimensionless Parameter scaling techniques. Previous experiments on the DIII-D tokamak have measured the variation of heat transport with the relative gyroradius ({rho}*); in this paper, the scaling of heat transport with plasma beta ({beta}) and normalized collisionality ({nu}) for L-mode and H-mode plasmas on the DIII-D tokamak is reported. Following the scale invariance approach to confinement scaling, the thermal diffusivity ({chi}) is assumed to depend only on local Dimensionless quantities. Understanding the beta and collisionality scaling of transport helps to differentiate between various proposed mechanisms of turbulent transport and allows the origin of power degradation and density scaling of confinement to be determined.
-
Implications from Dimensionless Parameter scaling experiments
1996Co-Authors: T.c. Luce, B. Balet, C.c. Petty, J.g. CordeyAbstract:The Dimensionless Parameter scaling approach is increasingly useful for predicting future tokamak performance and guiding theoretical models of energy transport. Experiments to determine the {rho}* (gyroradius normalized to plasma size) scaling have been carried out in many regimes. The electron {rho}* scaling is always ``gyro-Bohm``, while the ion {rho}* scaling varied with regime. The ion variation is correlated with both density scale length (L mode, H mode) and current profile. The ion {rho}* scaling in the low-q, H-mode regime is gyro-Bohm, which is the most favorable confinement scaling observed. New experiments in {beta} scaling and collisionality scaling have been carried out in low-q discharges in both L mode and H mode. In L mode, global analysis shows that there is a slightly unfavorable {beta} dependence ({beta}{sup {minus}0.1}) and no {nu}* dependence. In H-mode, global analysis finds a weak {beta} dependence ({beta}{sup 0.1}) and an unfavorable dependence on {nu}*. The lack of significant {beta} scaling spans the range of {beta}{sub N} from 0.25 to 2.0. The very small {beta} dependence in L mode and H mode is in contradiction with the standard global scaling relations. This contradiction in H mode may be indicative of the impact on the H-mode database ofmore » low-n tearing instabilities which are observed at slightly higher {beta}{sub N} in the {beta} scaling experiments. The measured {beta} and {nu}* scalings explain the weak density dependence observed in engineering Parameter scans. It also points to the power of the Dimensionless Parameter approach, since it is possible to obtain a definitive size scaling from experiments on a single tokamak.« less
T.c. Luce - One of the best experts on this subject based on the ideXlab platform.
-
application of Dimensionless Parameter scaling techniques to the design and interpretation of magnetic fusion experiments
Plasma Physics and Controlled Fusion, 2008Co-Authors: T.c. Luce, C.c. Petty, J.g. CordeyAbstract:A review of the application of Dimensionless Parameter scaling techniques to magnetic fusion experiments is presented. Because the methods of this type of analysis are not generally known, a detailed discussion of the basis for these techniques is given, including examples. The primary applications and successes of these methods in magnetic fusion research are in the area of transport of energy and particles across surfaces of constant magnetic flux. The experimental justification for the use of these techniques to describe transport is given, and the applications are reviewed. The two key applications of these techniques, the identification of the underlying physical mechanisms that cause transport and the projection of the transport in future devices from present-day experiments, are extensively discussed. Comparison of the results of Dimensionless Parameter scaling experiments with the regression analysis of multi-machine databases points to limitations in the databases and the analysis of them as the source of the discrepancies. These discrepancies have significant implications for the design optimization of tokamaks, which are discussed here. Finally, the application of Dimensionless Parameter scaling techniques to plasma stability, to the boundary region between closed and open field lines and to divertor operation in the open field line region are reviewed and discussed.
-
Experimental constraints on transport from Dimensionless Parameter scaling studies
Physics of Plasmas, 1998Co-Authors: C.c. Petty, J.g. Cordey, T.c. Luce, D.r. Baker, B. Ballet, T. N. Carlstrom, J.c. Deboo, P. Gohil, R.j. Groebner, B. W. RiceAbstract:The scalings of heat transport with safety factor (q), normalized collisionality (v), plasma beta ({beta}), and relative gyroradius ({rho}*) have been measured on the DIII-D tokamak. The measured {rho}* {beta} and v scalings of heat transport indicate that E x B transport from drive wave turbulence is a plausible basis for anomalous transport. For high confinement (H) mode plasmas where the safety factor was varied at fixed magnetic shear, the effective (or one-fluid) thermal diffusivity was found to scale like {chi}{sub eff} {proportional_to} q{sup 2.3{+-}0.64}, with the ion and electron fluids having the same q scaling to within the experimental errors except near the plasma edge. The scaling of the thermal confinement time with safety factor was in good agreement with this local transport dependence, {tau}{sub th} {proportional_to} q{sup {minus}2.42{+-}0.31}; however, when the magnetic shear was allowed to vary to keep q{sub 0} fixed during the (edge) safety factor scan, a weaker global dependence was observed, {tau}{sub th} {proportional_to} q{sub 95}{sup {minus}1.43{+-}0.23}. This weaker dependence was mainly due to the change in the local value of q between the two types of scans. The combined {rho}*, {beta}, v and q scalings of heat transport for H-mode plasmas on DIII-D reproduce the empirical confinement scaling using physical (Dimensionless) Parameters with the exception of weaker power degradation.
-
Understanding transport through Dimensionless Parameter scaling experiments
1997Co-Authors: C.c. Petty, T.c. LuceAbstract:The related methods of dimensional analysis, similarity, and scale invariance provide a powerful technique for analyzing physical systems. For example, the complex plasma dynamics governed by the Vlasov-Maxwell system of equations can be characterized by sets of Dimensionless quantities through the application of these techniques. Significant progress has been made recently towards predicting and understanding radial heat transport using Dimensionless Parameter scaling techniques. Previous experiments on the DIII-D tokamak have measured the variation of heat transport with the relative gyroradius ({rho}*); in this paper, the scaling of heat transport with plasma beta ({beta}) and normalized collisionality ({nu}) for L-mode and H-mode plasmas on the DIII-D tokamak is reported. Following the scale invariance approach to confinement scaling, the thermal diffusivity ({chi}) is assumed to depend only on local Dimensionless quantities. Understanding the beta and collisionality scaling of transport helps to differentiate between various proposed mechanisms of turbulent transport and allows the origin of power degradation and density scaling of confinement to be determined.
-
Implications from Dimensionless Parameter scaling experiments
1996Co-Authors: T.c. Luce, B. Balet, C.c. Petty, J.g. CordeyAbstract:The Dimensionless Parameter scaling approach is increasingly useful for predicting future tokamak performance and guiding theoretical models of energy transport. Experiments to determine the {rho}* (gyroradius normalized to plasma size) scaling have been carried out in many regimes. The electron {rho}* scaling is always ``gyro-Bohm``, while the ion {rho}* scaling varied with regime. The ion variation is correlated with both density scale length (L mode, H mode) and current profile. The ion {rho}* scaling in the low-q, H-mode regime is gyro-Bohm, which is the most favorable confinement scaling observed. New experiments in {beta} scaling and collisionality scaling have been carried out in low-q discharges in both L mode and H mode. In L mode, global analysis shows that there is a slightly unfavorable {beta} dependence ({beta}{sup {minus}0.1}) and no {nu}* dependence. In H-mode, global analysis finds a weak {beta} dependence ({beta}{sup 0.1}) and an unfavorable dependence on {nu}*. The lack of significant {beta} scaling spans the range of {beta}{sub N} from 0.25 to 2.0. The very small {beta} dependence in L mode and H mode is in contradiction with the standard global scaling relations. This contradiction in H mode may be indicative of the impact on the H-mode database ofmore » low-n tearing instabilities which are observed at slightly higher {beta}{sub N} in the {beta} scaling experiments. The measured {beta} and {nu}* scalings explain the weak density dependence observed in engineering Parameter scans. It also points to the power of the Dimensionless Parameter approach, since it is possible to obtain a definitive size scaling from experiments on a single tokamak.« less
Metin Kök - One of the best experts on this subject based on the ideXlab platform.
-
Influence of Dimensionless Parameter on De-Ionized Water-alumina Nanofluid Based Parabolic Trough Solar Collector.
Recent patents on nanotechnology, 2020Co-Authors: Vijayan Gopalsamy, Karunakaran Rajasekaran, Logesh Kamaraj, Siva Sivasaravanan, Metin KökAbstract:Background Aqueous-alumina nanofluid was prepared using magnetic stirrer and ultrasonication process. Then, the prepared nanofluid was subjected to flow through the unshielded receiver of the parabolic trough solar collector to investigate the performance of the nanofluid and the effects of the Dimensionless Parameter were determined. Methods The experimental work has been divided into two sections. First, the nanofluid was prepared and tested for its morphology, dimensions, and sedimentation using X-Ray Diffraction and Raman shift method. Then, the nanofluids of various concentrations from 0 to 4.0% are used as heat transfer fluid in unshielded type collector. Finally, the effect of the Dimensionless Parameter on the performance was determined. Results For the whole test period, depending upon the bulk mean temperature, the Dimensionless Parameters such as Re and Nu varied from 1098 to 4552 & 19.30 to 46.40 for air and 2150 to 7551 & 11.11 to 48.54 for nanofluid. The enhancement of thermal efficiency found for 0% and 4.0% nanoparticle concentrations was 32.84% for the mass flow rate of 0.02 kg/s and 13.26% for the mass flow rate of 0.06 kg/s. Conclusion Re and Nu of air depend on air velocity and ambient temperature. Re increased with the mass flow rate and decreased with concentration. Heat loss occurred by convection mode of heat transfer. Heat transfer coefficient and global efficiency increased with increased mass flow rate and volume fraction. The thermal efficiency of both 0% and 4.0% concentrations became equal for increased mass flow rate. It has been proven that at high mass flow rates, the time available to absorb the heat energy from the receiver is insufficient.
B. W. Rice - One of the best experts on this subject based on the ideXlab platform.
-
Experimental constraints on transport from Dimensionless Parameter scaling studies
Physics of Plasmas, 1998Co-Authors: C.c. Petty, J.g. Cordey, T.c. Luce, D.r. Baker, B. Ballet, T. N. Carlstrom, J.c. Deboo, P. Gohil, R.j. Groebner, B. W. RiceAbstract:The scalings of heat transport with safety factor (q), normalized collisionality (v), plasma beta ({beta}), and relative gyroradius ({rho}*) have been measured on the DIII-D tokamak. The measured {rho}* {beta} and v scalings of heat transport indicate that E x B transport from drive wave turbulence is a plausible basis for anomalous transport. For high confinement (H) mode plasmas where the safety factor was varied at fixed magnetic shear, the effective (or one-fluid) thermal diffusivity was found to scale like {chi}{sub eff} {proportional_to} q{sup 2.3{+-}0.64}, with the ion and electron fluids having the same q scaling to within the experimental errors except near the plasma edge. The scaling of the thermal confinement time with safety factor was in good agreement with this local transport dependence, {tau}{sub th} {proportional_to} q{sup {minus}2.42{+-}0.31}; however, when the magnetic shear was allowed to vary to keep q{sub 0} fixed during the (edge) safety factor scan, a weaker global dependence was observed, {tau}{sub th} {proportional_to} q{sub 95}{sup {minus}1.43{+-}0.23}. This weaker dependence was mainly due to the change in the local value of q between the two types of scans. The combined {rho}*, {beta}, v and q scalings of heat transport for H-mode plasmas on DIII-D reproduce the empirical confinement scaling using physical (Dimensionless) Parameters with the exception of weaker power degradation.