Abstract: A particle image velocimetry system is provided which supplies tracer particles to a flow field around an object (12) from tracer particle supply means, takes an image of reflected light by imaging means (32A, 32B) by irradiating the tracer particles twice with laser light at different times, and determines a velocity vector of the flow field based on the two images obtained of the tracer particles. The two images are each divided into a plurality of test regions, and when first peak value (fp)/second peak value (sp)?1.2 is satisfied by comparison between a first peak value fp and a second peak value sp of a cross-correlation value of a luminance pattern of tracer particles in each test region of the two images, it is determined that the reliability of the velocity vector is high. Thus, it is possible to enhance the precision of measurement of the state of flow by reliably determining erroneous vectors.

Abstract: A device for measuring a sound source distribution in three-dimensional space is provided in which tracer particles included around an object are irradiated with a two-dimensional laser sheet within an x-y plane at two times separated by a short time interval, images of the irradiated tracer particles are taken, and two in-plane velocity components of the tracer particles in the laser sheet and one out-of-plane velocity component perpendicular to the laser sheet are measured based on the images taken. Further, the velocity field of the three velocity components in three-dimensional space is measured by obtaining three velocity components within a plurality of planes spaced apart in a z-axis direction perpendicular to the laser sheet and stacking the three velocity components within the plurality of planes in the z-axis direction. The sound source distribution around the object is measured from the velocity field.

Abstract: An aerodynamic noise reduction device reduces aerodynamic noise originating from a separation region located downstream of a step portion protruding from a surface of an object placed in an airflow. Since the step portion protrudes from the surface of the object placed in the airflow, aerodynamic noise is generated from the airflow separation region located downstream of the step portion. However, by forming an air discharge vent at the step portion at a position near a point, in the separation region, where a Reynolds stress is at its maximum and by discharging air from the air discharge vent toward the point where the Reynolds stress is at its maximum, the velocity gradient in the separated shear layer in the separation region is mitigated to decrease the maximum value of the Reynolds stress. The aerodynamic noise is thus effectively reduced.

Abstract: An aerodynamic noise reduction device reduces aerodynamic noise originating from a separation region located downstream of a step portion protruding from a surface of an object placed in an airflow. Since the step portion protrudes from the surface of the object placed in the airflow, aerodynamic noise is generated from the airflow separation region located downstream of the step portion. However, by forming an air discharge vent at the step portion at a position near a point, in the separation region, where a Reynolds stress is at its maximum and by discharging air from the air discharge vent toward the point where the Reynolds stress is at its maximum, the velocity gradient in the separated shear layer in the separation region is mitigated to decrease the maximum value of the Reynolds stress. The aerodynamic noise is thus effectively reduced.

Abstract: A device for measuring a sound source distribution in three-dimensional space is provided in which tracer particles included in a steady flow around an object (12) are irradiated with a two-dimensional laser sheet (Ls) within an x-y plane at two times having a very short time interval, images of the irradiated tracer particles are taken from two intersecting directions in the laser sheet (Ls) by imaging means (32A, 32B), and two in-plane velocity components of the tracer particles in the laser sheet (Ls) and one out-of-plane velocity component perpendicular to the laser sheet (Ls) are measured based on the images taken at the two times. Further, the velocity field of the three velocity components in three-dimensional space is measured by obtaining three velocity components within a plurality of planes spaced apart in a z-axis direction perpendicular to the laser sheet (Ls) and stacking the three velocity components within the plurality of planes in the z-axis direction.

Abstract: A particle image velocimetry system is provided which supplies tracer particles to a flow field around an object (12) from tracer particle supply means, takes an image of reflected light by imaging means (32A, 32B) by irradiating the tracer particles twice with laser light at different times, and determines a velocity vector of the flow field based on the two images obtained of the tracer particles. The two images are each divided into a plurality of test regions, and when first peak value (fp)/second peak value (sp)?1.2 is satisfied by comparison between a first peak value fp and a second peak value sp of a cross-correlation value of a luminance pattern of tracer particles in each test region of the two images, it is determined that the reliability of the velocity vector is high. Thus, it is possible to enhance the precision of measurement of the state of flow by reliably determining erroneous vectors.

Abstract: At least part of the inner circumferential wall of the outer casing is provided with a concave surface opposing the rotor blade tips as seen in a longitudinal section. Typically, each of the rotor blades is provided with aerofoil section, and the compressor is designed as a transonic axial flow compressor. Thereby, a compressive wave is produced upstream of the shockwave so that the Mach number of the flow entering the shockwave can be reduced. As a result, the shockwave is made less severe, and the shockwave loss can be reduced. In particular, because the concave surface is provided in the casing wall as opposed to the case where the concave surface is provided in the negative pressure side of the rotor blade, the reduction in the performance owing to the change in the angle of the airflow entering the passage defined by the concave surface under a partial load condition can be avoided.

Abstract: In an axial flow compressor, an apical angle at a leading edge of a stator blade progressively increases from a root end to a tip of the stator blade whereby the stator blade loss and noises caused by unsteady inter-blade airflow can be minimized. Preferably, the apical angle at the tip of the stator blade is 1.5 to 2.5 times of the apical angle at the root of the stator blade.

Abstract: In an axial flow compressor, an apical angle at a leading edge of a stator blade progressively increases from a root end to a tip of the stator blade whereby the stator blade loss and noises caused by unsteady inter-blade airflow can be minimized. Preferably, the apical angle at the tip of the stator blade is 1.5 to 2.5 times of the apical angle at the root of the stator blade.

Abstract: At least part of the inner circumferential wall of the outer casing is provided with a concave surface opposing the rotor blade tips as seen in a longitudinal section. Typically, each of the rotor blades is provided with aerofoil section, and the compressor is designed as a transonic axial flow compressor. Thereby, a compressive wave is produced upstream of the shockwave so that the Mach number of the flow entering the shockwave can be reduced. As a result, the shockwave is made less severe, and the shockwave loss can be reduced. In particular, because the concave surface is provided in the casing wall as opposed to the case where the concave surface is provided in the negative pressure side of the rotor blade, the reduction in the performance owing to the change in the angle of the airflow entering the passage defined by the concave surface under a partial load condition can be avoided.