Combinational Influence of Internal Flow and External Annular Axial Flow on Instability of Cantilevered Double Wall Pipes

2017 ◽  
Author(s):  
Katsuhisa Fujita ◽  
Akinori Moriasa
Keyword(s):  
Dynamic Stability ◽  
Flow Direction ◽  
Fluid Velocity ◽  
Axial Flow ◽  
Internal Flow ◽  
External Flow ◽  
Elastic Tube ◽  
Piping System ◽  
Navier Stokes Equation ◽  
Double Wall

When flexible pipes are subjected to internal flow, the pipes lose stability by flutter and divergence in increasing the fluid velocity. In addition, they also lose stability when they are subjected to external annular axial flow. In this paper, the pipe is subjected to internal flow and external flow at the same time. The dynamic stability of a double wall pipe structure system subjected to an internal flow and an external flow simultaneously is thought to be one of the important pipe structures for the development of a piping system in the field of ocean mining, and in the field of fluid energy generation, and so on. In this paper, the pipe structures are assumed to be composed of the cantilevered elastic tube structure. For the analysis of the internal flow, the conventional inviscid stability analysis method is applied. For the analysis of the external annular axial flow, both the viscous solution using the Navier-Stokes equation of motion and the ideal fluid solution which viscous influence are added to are applied. Changing the flow direction and the fluid velocity as for the internal flow and the external flow, the dynamic stability of the double wall pipes is investigated and discussed. Moreover, changing the flow rate and the density of a fluid and a structure, these effects on the stability of double wall pipes are investigated.

Stability of Cantilevered Pipes Subjected to Internal Flow and External Annular Axial Flow Simultaneously

2015 ◽  
Author(s):  
Katsuhisa Fujita ◽  
Akinori Moriasa
Keyword(s):  
Flow Direction ◽  
Fluid Velocity ◽  
Axial Flow ◽  
Internal Flow ◽  
External Flow ◽  
Energy Utilization ◽  
Navier Stokes ◽  
Piping System ◽  
Navier Stokes Equation ◽  
Cantilevered Beam

When slender pipes are subjected to internal flow, the pipes lose stability by flutter and divergence in increasing the fluid velocity. In addition, they also lose stability when they are subjected to external annular axial flow. In the development of a piping system in the field of ocean mining, and in the field of fluid energy utilization, and so forth, the double walled pipe structure system subjected to an internal flow and an external flow simultaneously is thought to be one of the important pipe structures. In this paper, the pipe structures are assumed to be composed of the cantilevered beam structure which shows the complicated dynamic behavior than the other supported conditions. For the analysis of the internal flow, the conventional inviscid stability analysis method is applied. For the analysis of the external annular axial flow, both the viscous solution using the Navier-Stokes equation of motion and the ideal fluid solution which viscous influence is added to are applied. Changing the flow direction and the fluid velocity of the internal flow and the external flow, and the specifications of modeling, the stability of the double walled pipes is investigated and discussed.

Numerical Analysis of Flow Field Characteristics in Three-Z-Shaped Ultrasonic Flowmeter

2012 ◽  
Vol 226-228 ◽  
pp. 1829-1834 ◽  
Author(s):  
Jing Yuan Tang ◽  
Jian Ming Chen ◽  
Hong Bin Ma ◽  
Guang Yu Tang
Keyword(s):  
Flow Field ◽  
Cross Sections ◽  
Flow Direction ◽  
Fluid Velocity ◽  
Internal Flow ◽  
Reynolds Stress Model ◽  
Ultrasonic Flowmeter ◽  
Developed Turbulence ◽  
Fluid Field ◽  
Flow Field Characteristics

The flow field characteristics in U-typed bend has been extensively studied for transit time ultrasonic flowmeters designing, but for the flowmeter with three-Z-shaped round pipe there is still lack of corresponding research. This paper presents a computational fluid dynamics (CFD) approach for modeling of the three-Z-shaped ultrasonic flowmeter and studying of internal fluid field characteristics based on Reynolds stress model (RSM). The fluid velocity profile in the three ultrasound path is obtained using CFD and secondary flow in cross section also is analyzed. The simulation results show that the internal flow fields in the flowmeter are not fully developed turbulence with asymmetric axial velocity distribution and dramatic changes along the flow direction, and there are obvious secondary cross flows on theirs cross-sections. The CFD simulations provide useful insights into the flow field associated with ultrasonic flowmeters design.

Nonlinear Dynamics of an Extensible Flexible Pipe Conveying Fluid and Subjected to External Axial Flow

2011 ◽  
Author(s):  
F. A. Ghaith ◽  
Y. A. Khulief
Keyword(s):  
Nonlinear Equations ◽  
Linear Models ◽  
Numerical Solutions ◽  
Plug Flow ◽  
Axial Flow ◽  
Internal Flow ◽  
External Flow ◽  
Pipe Conveying Fluid ◽  
Flexible Pipe ◽  
Conveying Fluid

In this paper, the nonlinear equations representing the dynamics of a slender flexible pipe conveying fluid and subjected to external axial flow are formulated using the extended Hamilton’s principle. The internal flow is assumed to be steady, fully developed turbulent and approximated by a plug flow, while the external flow is represented by the induced hydrodynamic forces associated with friction, hydrostatic and inviscid components. The pipe centerline is considered to be extensible, and hence two coupled nonlinear equations of motion associated with longitudinal and transverse displacements are derived to describe the dynamics of the system. The developed model takes into account the fluid pressurization force and the tension in the pipe, which may be externally applied or associated with the frictional forces. For verification purpose, comparisons were performed, wherein the developed formulation was reduced to some published linear models. Numerical solutions were obtained for a case study of a double-pipe heat exchanger, wherein the effects of internal flow, external flow, flowrate, and radial gap on the dynamic characteristics of the system were addressed.

Dynamics of Slender Tapered Beams With Internal or External Axial Flow—Part 1: Theory

1979 ◽  
Vol 46 (1) ◽  
pp. 45-51 ◽  
Author(s):  
M. J. Hannoyer ◽  
M. P. Paidoussis
Keyword(s):  
Boundary Layer ◽  
Boundary Layer Thickness ◽  
Equations Of Motion ◽  
Axial Flow ◽  
Internal Flow ◽  
External Flow ◽  
High Flow ◽  
Flow Passage ◽  
Flow Part ◽  
Surrounding Fluid

This paper develops a general theory for the dynamics of slender, nonuniform axisymmetric beams subjected to either internal or external flow, or to both simultaneously. The effect of the boundary layer of the external flow is taken into account in the formulation. Typical solutions of the equations of motion are presented for cantilevered conical beams in external flow and for beams with a conical internal flow passage. Such systems lose stability at sufficiently high flow velocity, internal or external, either by flutter or by buckling. The effect of several parameters is investigated. For internal flow, the internal and external shape, whether uniform or conical, and the density of the surrounding fluid have sometimes unexpected effects on stability; e.g., tubular beams lose stability at lower internal flow when immersed in water than when in air. For external flow the effects of conicity, free end shape and boundary-layer thickness are investigated; the latter has a strong stabilizing influence, such that simple theory neglecting this effect results in serious error.

Dynamics of Slender Tapered Beams With Internal or External Axial Flow—Part 2: Experiments

1979 ◽  
Vol 46 (1) ◽  
pp. 52-57 ◽  
Author(s):  
M. J. Hannoyer ◽  
M. P. Paidoussis
Keyword(s):  
Axial Flow ◽  
Internal Flow ◽  
Quantitative Agreement ◽  
External Flow ◽  
Critical Conditions ◽  
Experimental Program ◽  
Water Tunnel ◽  
Elastic Instabilities ◽  
Theoretical Predictions ◽  
Flow Part

This paper describes the experimental program which was conducted in parallel with the theoretical investigation presented in Part 1 of this study. Experiments were conducted in a special water tunnel with silicone rubber cantilevers which, in the case of external flow, were truncated cones, the free ends of which were streamlined; in the case of internal flow the beams were tubular, conical inside, and either conical or cylindrical outside, immersed either in still air or water. Experiments were also conducted with uniform tubular cylinders, and some with simultaneous internal and external axial flow. Qualitatively these experiments support theoretical predictions very well. The critical conditions for the various fluid-elastic instabilities which these systems can develop were measured and compared with theory. Quantitative agreement ranged from excellent to fair, the former for internal flow in conical tubes, and the latter for very slender cones in external flow.

Influence on the Axial Flow Fan Aerodynamic Characteristic Due to an Introduction of Internal Secondary Flow

2008 ◽  
Author(s):  
Matjazˇ Eberlinc ◽  
Brane Sˇirok ◽  
Marko Hocˇevar ◽  
Matevzˇ Dular
Keyword(s):  
Standardized Test ◽  
Flow Direction ◽  
Axial Flow ◽  
Performance Testing ◽  
Internal Flow ◽  
Suction Side ◽  
Flow Conditions ◽  
Axial Fan ◽  
Trailing Edge ◽  
Local Characteristics

Axial fans often show adverse flow conditions at the fan hub and at the tip of the blades. Modification of conventional axial fan blades is presented. Hollow blades were manufactured from the hub to the trailing edge at the tip of the blades. Hollow blades enabled the formation of self-induced internal flow through internal passages. The internal flow enters the internal radial flow passages of the hollow blades through the openings near the fan hub and exits through the tip trailing edge slots. Study of the influence of internal flow on the flow field of axial fan and modifications of axial fan aerodynamic characteristics is presented. The characteristics of the axial fan with the internal flow were compared to characteristics of a geometrically equivalent fan without internal flow. The results show integral measurements of performance testing using standardized test rig, and the measurements of local characteristics. The measurements of local characteristics were performed with a hot-wire anemometry, five-hole probe and computer-aided visualization. We attained reduction of adverse flow conditions near the blade tip trailing edge, boundary-layer reduction on the blade suction side and reduction of flow separation. Introduction of the self-induced blowing led to the preservation of external flow direction, defined by blade geometry and enabled maximal local energy conversion. The integral characteristic reached higher degree of efficiency.

Improvement of Stalling Characteristics of an Axial-Flow Fan by Radial-Vaned Air-Separators

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
Nobuyuki Yamaguchi ◽  
Masayuki Ogata ◽  
Yohei Kato
Keyword(s):  
Solid Wall ◽  
Axial Flow ◽  
Internal Flow ◽  
Rotor Blades ◽  
Relative Location ◽  
Flow Conditions ◽  
Axial Flow Fan ◽  
Light Load ◽  
Stall Prevention ◽  
Air Separator

An improved construction of air-separator device, which has radial-vanes embedded within its inlet circumferential opening with their leading-edges facing the moving tips of the fan rotor-blades so as to scoop the tip flow, was investigated with respect to the stall-prevention effect on a low-speed, single-stage, lightly loaded, axial-flow fan. Stall-prevention effects by the separator layout, relative location of the separator to the rotor-blades, and widths of the openings of the air-separator inlet and exit were parametrically surveyed. As far as the particular fan is concerned, the device together with the best relative location has proved to be able to eliminate effectively the stall zone having existed in the original solid-wall characteristics, which has confirmed the promising potential of the device. Guidelines were obtained from the data for optimizing relative locations of the device to the rotor-blades, maximizing the stall-prevention effect of the device, and minimizing the axial size of the device for a required stall-prevention effect, at least for the particular fan and possibly for fans of similar light-load fans. The data suggest the changing internal flow conditions affected by the device conditions.

On steady compressible flows with compact vorticity; the compressible Hill's spherical vortex

1998 ◽  
Vol 374 ◽  
pp. 285-303 ◽  
Author(s):  
D. W. MOORE ◽  
D. I. PULLIN
Keyword(s):  
Finite Difference ◽  
Compressible Flows ◽  
Numerical Solutions ◽  
Flow Direction ◽  
Fluid Velocity ◽  
Major Axis ◽  
Sonic Point ◽  
Euler Flow ◽  
Compressible Euler ◽  
Spherical Vortex

We consider steady compressible Euler flow corresponding to the compressible analogue of the well-known incompressible Hill's spherical vortex (HSV). We first derive appropriate compressible Euler equations for steady homentropic flow and show how these may be used to define a continuation of the HSV to finite Mach number M∞=U∞/C∞, where U∞, C∞ are the fluid velocity and speed of sound at infinity respectively. This is referred to as the compressible Hill's spherical vortex (CHSV). It corresponds to axisymmetric compressible Euler flow in which, within a vortical bubble, the azimuthal vorticity divided by the product of the density and the distance to the axis remains constant along streamlines, with irrotational flow outside the bubble. The equations are first solved numerically using a fourth-order finite-difference method, and then using a Rayleigh–Janzen expansion in powers of M2∞ to order M4∞. When M∞>0, the vortical bubble is no longer spherical and its detailed shape must be determined by matching conditions consisting of continuity of the fluid velocity at the bubble boundary. For subsonic compressible flow the bubble boundary takes an approximately prolate spheroidal shape with major axis aligned along the flow direction. There is good agreement between the perturbation solution and Richardson extrapolation of the finite difference solutions for the bubble boundary shape up to M∞ equal to 0.5. The numerical solutions indicate that the flow first becomes locally sonic near or at the bubble centre when M∞≈0.598 and a singularity appears to form at the sonic point. We were unable to find shock-free steady CHSVs containing regions of locally supersonic flow and their existence for the present continuation of the HSV remains an open question.

Coriolis force influence on the AKA effect

2021 ◽  
Author(s):  
Peter Rutkevich ◽  
Georgy Golitsyn ◽  
Anatoly Tur
Keyword(s):  
Steady State ◽  
Stokes Equation ◽  
Nonlinear Equations ◽  
Coriolis Force ◽  
Large Scale ◽  
Fluid Velocity ◽  
Navier Stokes ◽  
Basic Solution ◽  
Navier Stokes Equation ◽  
Alpha Effect

<p>Large-scale instability in incompressible fluid driven by the so called Anisotropic Kinetic Alpha (AKA) effect satisfying the incompressible Navier-Stokes equation with Coriolis force is considered. The external force is periodic; this allows applying an unusual for turbulence calculations mathematical method developed by Frisch et al [1]. The method provides the orders for nonlinear equations and obtaining large scale equations from the corresponding secular relations that appear at different orders of expansions. This method allows obtaining not only corrections to the basic solutions of the linear problem but also provides the large-scale solution of the nonlinear equations with the amplitude exceeding that of the basic solution. The fluid velocity is obtained by numerical integration of the large-scale equations. The solution without the Coriolis force leads to constant velocities at the steady-state, which agrees with the full solution of the Navier-Stokes equation reported previously. The time-invariant solution contains three families of solutions, however, only one of these families contains stable solutions. The final values of the steady-state fluid velocity are determined by the initial conditions. After account of the Coriolis force the solutions become periodic in time and the family of solutions collapses to a unique solution. On the other hand, even with the Coriolis force the fluid motion remains two-dimensional in space and depends on a single spatial variable. The latter fact limits the scope of the AKA method to applications with pronounced 2D nature. In application to 3D models the method must be used with caution.</p><p>[1] U. Frisch, Z.S. She and P. L. Sulem, “Large-Scale Flow Driven by the Anisotropic Kinetic Alpha Effect,” Physica D, Vol. 28, No. 3, 1987, pp. 382-392.</p>

Sign in / Sign up

Export Citation Format

Share Document