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Rajiv R. P. Singh - One of the best experts on this subject based on the ideXlab platform.

  • Magnetic order in coupled spin-Half and spin-one Heisenberg chains in an anisotropic triangular-lattice geometry
    Physical Review B, 2008
    Co-Authors: Tommaso Pardini, Rajiv R. P. Singh
    Abstract:

    We study spin-Half and spin-one Heisenberg Models in the limit where one-dimensional (1D) linear chains, with exchange constant ${J}_{1}$, are weakly coupled in an anisotropic triangular-lattice geometry. Results are obtained by means of linked-cluster series expansions at zero temperature around different magnetically ordered phases. We study the noncollinear spiral phases that arise classically in the Model and the collinear antiferromagnet that has been recently proposed for the spin-Half Model by Starykh and Balents [Phys. Rev. Lett. 98, 077205 (2007)] using a renormalization group approach. We find some evidence that such phases can be stabilized in the spin-Half Model for arbitrarily small coupling between the chains, though convergence of the sublattice-magnetization series remains unsatisfactory. For vanishing coupling between the chains the energy of each phase must approach that of decoupled linear chains. With increasing interchain coupling, the noncollinear phase appears to have a lower energy in our calculations. For the spin-one chain, we find that there is a critical interchain coupling needed to overcome the Haldane gap. When spin-one chains are coupled in the frustrated triangular-lattice geometry, the critical coupling required to close the Haldane gap is enhanced by an order of magnitude compared to unfrustrated interchain couplings in the square-lattice geometry. The collinear phase is not obtained for the spin-one Heisenberg Model.

Christian Klein - One of the best experts on this subject based on the ideXlab platform.

  • Recent Developments of PSP and TSP at DLR for Application to Transonic Flows in Industrial Wind Tunnels
    2008
    Co-Authors: Christian Klein
    Abstract:

    The pressure sensitive paint (PSP system is an optical measurement technique to investigate absolute pressure fields on Model surfaces for basic research in laboratories, industrial wind tunnels or high speed rotating turbo machines. Detailed qualitative and quantitative information and understanding of flow phenomena can be obtained in speed ranges from U∞ =20 m/s up to Ma= 5.0. A number of investigations of problems of industrial interest in different speed ranges from low speed flow over transonic to trisonic and cryogenic flows have been realised and compared with conventional techniques like point wise pressure measurements, flow velocity field measurements (PIV), and qualitative visualization (laser light sheets). The influences of the main error sources for the components of the PSP system have been checked. Comparison of experimental pressure fields obtained by means of PSP and the results of numerical calculations have been carried out. Different wind tunnel Models ranging from basic configurations such as a cropped delta wing to a complex Half Model of a large propeller-driven transport aircraft with all flaps, rudders and shrouds, and rotating or oscillating Models as well as Reynolds number effects by means of TSP on Models have been investigated.

  • Quantitative Wind Tunnel Studies Using Pressure- and Temperature Sensitive Paints
    Journal of Visualization, 2005
    Co-Authors: Rolf H. Engler, Christian Klein, Uwe Fey, Ulrich Henne, Werner Sachs
    Abstract:

    The pressure sensitive paint (PSP) intensity and lifetime system is an optical measurement technique to investigate absolute pressure fields on Model surfaces for basic research in laboratories, industrial wind tunnels or high speed rotating turbo machines. Detailed qualitative and quantitative information and understanding of flow phenomena can be obtained in speed ranges from U$_{∞}$=20 m/s up to Ma=5.0. A number of projects of industrial interest has been investigated in different wind tunnels covering low speed, transonic, trisonic and cryogenic facilities. The influence of the main error sources for the components of the PSP system have been checked. Comparison of experimental pressure fields obtained by means of PSP and the results of numerical calculations have been carried out. Different wind tunnel Models ranging from basic configurations such as a cropped delta wing to a complex Half Model of a large propeller-driven transport aircraft with all flaps, rudders and shrouds, and rotating or oscillating Models as well as Reynolds number effects on Models have been investigated.

  • Pressure Sensitive Paints and Temperature Sensitive Paints in Quantitative Wind Tunnel Studies
    2005
    Co-Authors: Rolf Engler, Christian Klein, Uwe Fey, Ulrich Henne, Werner Sachs
    Abstract:

    The pressure sensitive paint (PSP) intensity and lifetime system is an optical measurement technique to investigate absolute pressure fields on Model surfaces for basic research in laboratories, industrial wind tunnels or high speed rotating turbo machines. Detailed qualitative and quantitative information and understanding of flow phenomena can be obtained in speed ranges from U∞ = 20 m/s up to Ma = 5.0. A number of projects of industrial interest has been investigated in different wind tunnels covering low speed, transonic, trisonic and cryogenic facilities. The influence of the main error sources for the components of the PSP system have been checked. Comparison of experimental pressure fields obtained by means of PSP and the results of numerical calculations have been carried out. Different wind tunnel Models ranging from basic configurations such as a cropped delta wing to a complex Half Model of a large propeller-driven transport aircraft with all flaps, rudders and shrouds, and rotating or oscillating Models as well as Reynolds number effects on Models have been investigated.

  • Pressure sensitive paint systems for pressure distribution measurements in wind tunnels and turbomachines
    Measurement Science and Technology, 2000
    Co-Authors: Rolf H. Engler, Christian Klein, Ole Trinks
    Abstract:

    We have used the pressure-sensitive paint (PSP) intensity and lifetime methods for basic research and PSP measurements in wind tunnels and turbomachines, to investigate and understand the qualitative and quantitative aerodynamic measurements mainly in transonic flow. We performed a number of investigations in different speed ranges from transonic to low-speed flow and compared them with conventional techniques like pressure taps and light sheets. The influence of errors was checked and a comparison with numerical methods performed. Various Models were investigated, from the basic configuration of a double-delta-wing up to a complex Airbus A340 Half Model and oscillating turbine blades. Finally, two excellent PSP systems are now available to perform precise measurements and support the theory using these techniques.

Naoki Saito - One of the best experts on this subject based on the ideXlab platform.

Werner Sachs - One of the best experts on this subject based on the ideXlab platform.

  • Pressure Sensitive Paints and Temperature Sensitive Paints in Quantitative Wind Tunnel Studies
    2005
    Co-Authors: Rolf Engler, Christian Klein, Uwe Fey, Ulrich Henne, Werner Sachs
    Abstract:

    The pressure sensitive paint (PSP) intensity and lifetime system is an optical measurement technique to investigate absolute pressure fields on Model surfaces for basic research in laboratories, industrial wind tunnels or high speed rotating turbo machines. Detailed qualitative and quantitative information and understanding of flow phenomena can be obtained in speed ranges from U∞ = 20 m/s up to Ma = 5.0. A number of projects of industrial interest has been investigated in different wind tunnels covering low speed, transonic, trisonic and cryogenic facilities. The influence of the main error sources for the components of the PSP system have been checked. Comparison of experimental pressure fields obtained by means of PSP and the results of numerical calculations have been carried out. Different wind tunnel Models ranging from basic configurations such as a cropped delta wing to a complex Half Model of a large propeller-driven transport aircraft with all flaps, rudders and shrouds, and rotating or oscillating Models as well as Reynolds number effects on Models have been investigated.

  • Quantitative Wind Tunnel Studies Using Pressure- and Temperature Sensitive Paints
    Journal of Visualization, 2005
    Co-Authors: Rolf H. Engler, Christian Klein, Uwe Fey, Ulrich Henne, Werner Sachs
    Abstract:

    The pressure sensitive paint (PSP) intensity and lifetime system is an optical measurement technique to investigate absolute pressure fields on Model surfaces for basic research in laboratories, industrial wind tunnels or high speed rotating turbo machines. Detailed qualitative and quantitative information and understanding of flow phenomena can be obtained in speed ranges from U$_{∞}$=20 m/s up to Ma=5.0. A number of projects of industrial interest has been investigated in different wind tunnels covering low speed, transonic, trisonic and cryogenic facilities. The influence of the main error sources for the components of the PSP system have been checked. Comparison of experimental pressure fields obtained by means of PSP and the results of numerical calculations have been carried out. Different wind tunnel Models ranging from basic configurations such as a cropped delta wing to a complex Half Model of a large propeller-driven transport aircraft with all flaps, rudders and shrouds, and rotating or oscillating Models as well as Reynolds number effects on Models have been investigated.

Shabudin Mat - One of the best experts on this subject based on the ideXlab platform.

  • FBG as air pressure sensors on generic UTM-LST Half Model
    Malaysian Journal of Fundamental and Applied Sciences, 2017
    Co-Authors: Muhammad Izuan, Shabudin Mat, Raja Kamarulzaman Raja Ibrahim, Asrul Izam Azmi
    Abstract:

    This work was done to investigate the feasibility of FBGs strain sensor in detection of air pressure on aeroplane Model known as Generic UTM Half-Model. The FBGs was attached on the surface of  aeroplane Model where its position is as near as possible to the location of static pressure sensor. Then, the sensing performance was tested inside UTM Low Speed Tunnel (UTM-LST) with the wind speed set at 30 , 40 , and 50 . The direction of wind was arranged to be in perpendicular to the sensing elements and the wing Model angle was varied at 0°, 5°, 10°, 15°, and 20°. The measured pressure coefficient, Cp based on Bragg wavelength shift was compared with FKPS 30DP Pressure Measuring Module data. The results shows that the shift in Bragg wavelength found to be linearly increased when the wind speed is increased. The pressure coefficient obtained by FBG has approximate value as the pressure coefficient of pressure sensor module at low angle of attack from 0° to 12°.

  • Experimental study of UTM-LST generic Half Model transport aircraft
    IOP Conference Series: Materials Science and Engineering, 2016
    Co-Authors: M I Ujang, Shabudin Mat, K Perumal, M. N. Mohd Nasir
    Abstract:

    This paper presents the experimental results from the investigation carried out at the UTM Low Speed wind tunnel facility (UTM-LST) on a Half Model generic transport aircraft at several configurations of primary control surfaces (flap, aileron and elevator). The objective is to measure the aerodynamic forces and moments due to the configuration changes. The study is carried out at two different speeds of 26.1 m/s and 43.1 m/s at corresponding Reynolds number of 1 × 106 and 2 × 106, respectively. Angle of attack of the Model is varied between -2o to 20o. For the flaps, the deflection applied is 0o, 5o and 10o. Meanwhile, for aileron and elevator, the deflection applied is between -10o and 10o. The results show the differences in aerodynamic characteristics of the aircraft at different control surfaces configurations. The results obtained indicate that a laminar separation bubble developed on the surface of the wing at lower angles of attack and show that the separation process is delayed when the Reynolds number is increased.

  • EXPERIMENTAL AND COMPUTATIONAL FLUID DYNAMIC (CFD) STUDIES ON Half-Model TRANSPORT AIRCRAFT
    2003
    Co-Authors: Iskandar Shah Ishak, Shabudin Mat, Tholudin Mat Lazim, Mohd. Zailani Awang
    Abstract:

    This paper aims to highlight the wind tunnel testing techniques and the Computational Fluid Dynamic (CFD) studies on a Half-Model aircraft configuration. A 9% scale generic Model of 130-seaters transport aircraft with a 1.028m semi-span is used for the experimental works. The experiment is conducted at Universiti Teknologi Malaysia – Low Speed Tunnel (UTM-LST) which is currently the largest tunnel of its kind in Malaysia with a test section of 2m (breadth) X 1.5m (height) X 5.8m (length) and the maximum wind speed of 80 m/s. The experimental is carried out with a Reynolds No. of 1.3 X 10 6 . In the CFD work, a commercial CFD code, Fluent 5.3 is used to simulate the aerodynamic characteristics of this subsonic transport aircraft. It is found that the result obtained from the wind tunnel testing is agreeable with the results simulated by the CFD. The experimental result also indicates that the curve of pitching moment coefficient versus angle of attack has a negative slope which depicts the aircraft is statically longitudinal stable.

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