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Bir yüzey panel yöntemi ile ağır yüklü gemi pervanelerinin hidrodinamik analizi

A Surface panel method for the hydrodynamic analysis of heavily loaded marine propellers

  1. Tez No: 39784
  2. Yazar: ALİCAN TAKİNACI
  3. Danışmanlar: PROF.DR. TARIK SABUNCU
  4. Tez Türü: Doktora
  5. Konular: Gemi Mühendisliği, Marine Engineering
  6. Anahtar Kelimeler: Belirtilmemiş.
  7. Yıl: 1994
  8. Dil: Türkçe
  9. Üniversite: İstanbul Teknik Üniversitesi
  10. Enstitü: Fen Bilimleri Enstitüsü
  11. Ana Bilim Dalı: Belirtilmemiş.
  12. Bilim Dalı: Belirtilmemiş.
  13. Sayfa Sayısı: 108

Özet

parabola. The panels are regrouped to form the sets of four neighbouring panels. It is also important to locate their orientation for the two way differentiation of the surface velocity potentials or the dipole potentials. Each panel keeps an array of four neighbouring panels. The derivative along the two directions (for propeller blade radial and circumferential directions) are then found using the expression. *' = 2as + b (4) By choosing the origin of four neighbouring panels at the control point of the centre panel, the derivative is simply found to be equal to the coefficient b of the parabola. From the steady state flow point of view, the shape of the wake is initially not known and the process of finding the proper wake shape (wake roll up) is often denoted as a“slight nonlinearity”in the solution process. In this thesis, two methods for finding the wake shape have been developed. One of them is the hydrodynamic pitch method (HPM), and the other one is the stream line method (SLM). The HPM uses circumferentially averaged axial and tangential velocities. Therefore the hydrodynamic pitch angle of the propeller slipstream (wake) can be obtained for latter iterations as, P = arctan tvA.^ vor - ve (5) where iT. and v8 denote respectively the mean axial and tangential perturbation velocities at a section of the propeller blade. In this method, the radial velocities on the propeller blade are assumed to have no effect on the slipstream and therefore, contractions do not occur in the propeller slipstream along the downstream direction. The SLM uses the stream lines of the propeller blades, hub and their wakes. These stream lines are calculated for each side of the propeller blade, i.e. upper and lower sides. The upper stream line calculation starts at“a sufficient distance”from the trailing edge along its normal direction. This distance can be calculated from the boundary layer thickness obtained from the amprical formulas for a flat plate at the trailing edge and multiplied by a factor obtained from the numerical experiments. A wake strip can be easily calculated after applying the same procedure for the lower streamline and taking the averaged values of upper and lower streamlines. By applying this technique for each radial location on the propeller blade, the new wake shape can be obtained for the latter iterations. The convergence of this method (SLM) is also sufficiently fast, i.e., three or four iterations suffice. Two methods that are mentioned above lead to slightly different results depending on the propeller blade loading. If the blade loading factor introduced by Burril (Kafalı (1983)), tc, is greater than 0.40,the SLM gives satisfactory results. On the other hand, in the case of 0.30 < t. < 0.40, satisfactory results are obtained by the HPM. In the xiv

Özet (Çeviri)

A SURFACE PANEL METHOD FOR THE HYDRODYNAMIC ANALYSIS OF HEAVILY LOADED MARINE PROPELLERS SUMMARY in recent years, propellers with various blade geometries such as a highly skewed propeller have been fitted to ships in order to reduce the propeller induced vibration and noise, ör to improve the propulsive perfbrmance of propeller. A reliable numerical method is indispensable for the design and analysis of such propellers. A number of propeller design and analysis methods based on lifting surface theories such as The Vortex Lattice Method (VLM) which could account for the extremely complicated geometries of recent marine propellers, have been developed. However, the propeller lifting surface methods are essentially based on the thin wing theory. Therefore, they are insufficient to predict the pressure distribution on the propeller including the hub effect. On the other hand, surface panel methods have been remarkably advanced in the field of aerodynamics and hydrodynamics for the design and analysis of three dimensional wings and bodies. The advantages of the panel methods över the lifting surface methods would be to allow more precise representations of a complicated wing body configuration of an aircraft. in the past two decades, the surface panel methods have been applied to the marine propellers including the ducted and the contra rotating propellers and also the advanced turboprop problems. There exist a wide variety of surface panel methods which employ different types of surface panels, singularity distributions, and boundary conditions. Most of the panel methods are based on the Douglas Neumann constant source method developed by Hess and Smith, in which the majör unknovra was the source strength determined from the boundary condition of zero normal velocity at a control point on each panel (Hess and Smith (1966), for lifting bodies, Hess (1972)). Another surface panel formulation has been developed by the application of Green's identity to determine the unknpwn potential strength. A panel method based on Green's identity was first introduced by Morino for general lifting bodies and then, is called Morino method ör Morino formulation. Morino and Kuo (1974). Morino, Chen and Kuo (1975). The Morino method generally produces a well behaved singularity distribution leading to a numerically stable solution and also overcomes some of the problems associated with the Douglas Neumann method on the thin and highly loaded surface. in the Morino method, the governing equations for the velocity potential representing the flow are well known. The velocity potential at any point on the surface of the body can be obtained by a surface integral över the body and wake : xiparabola. The panels are regrouped to form the sets of four neighbouring panels. It is also important to locate their orientation for the two way differentiation of the surface velocity potentials or the dipole potentials. Each panel keeps an array of four neighbouring panels. The derivative along the two directions (for propeller blade radial and circumferential directions) are then found using the expression. *' = 2as + b (4) By choosing the origin of four neighbouring panels at the control point of the centre panel, the derivative is simply found to be equal to the coefficient b of the parabola. From the steady state flow point of view, the shape of the wake is initially not known and the process of finding the proper wake shape (wake roll up) is often denoted as a“slight nonlinearity”in the solution process. In this thesis, two methods for finding the wake shape have been developed. One of them is the hydrodynamic pitch method (HPM), and the other one is the stream line method (SLM). The HPM uses circumferentially averaged axial and tangential velocities. Therefore the hydrodynamic pitch angle of the propeller slipstream (wake) can be obtained for latter iterations as, P = arctan tvA.^ vor - ve (5) where iT. and v8 denote respectively the mean axial and tangential perturbation velocities at a section of the propeller blade. In this method, the radial velocities on the propeller blade are assumed to have no effect on the slipstream and therefore, contractions do not occur in the propeller slipstream along the downstream direction. The SLM uses the stream lines of the propeller blades, hub and their wakes. These stream lines are calculated for each side of the propeller blade, i.e. upper and lower sides. The upper stream line calculation starts at“a sufficient distance”from the trailing edge along its normal direction. This distance can be calculated from the boundary layer thickness obtained from the amprical formulas for a flat plate at the trailing edge and multiplied by a factor obtained from the numerical experiments. A wake strip can be easily calculated after applying the same procedure for the lower streamline and taking the averaged values of upper and lower streamlines. By applying this technique for each radial location on the propeller blade, the new wake shape can be obtained for the latter iterations. The convergence of this method (SLM) is also sufficiently fast, i.e., three or four iterations suffice. Two methods that are mentioned above lead to slightly different results depending on the propeller blade loading. If the blade loading factor introduced by Burril (Kafalı (1983)), tc, is greater than 0.40,the SLM gives satisfactory results. On the other hand, in the case of 0.30 < t. < 0.40, satisfactory results are obtained by the HPM. In the xivA SURFACE PANEL METHOD FOR THE HYDRODYNAMIC ANALYSIS OF HEAVILY LOADED MARINE PROPELLERS SUMMARY in recent years, propellers with various blade geometries such as a highly skewed propeller have been fitted to ships in order to reduce the propeller induced vibration and noise, ör to improve the propulsive perfbrmance of propeller. A reliable numerical method is indispensable for the design and analysis of such propellers. A number of propeller design and analysis methods based on lifting surface theories such as The Vortex Lattice Method (VLM) which could account for the extremely complicated geometries of recent marine propellers, have been developed. However, the propeller lifting surface methods are essentially based on the thin wing theory. Therefore, they are insufficient to predict the pressure distribution on the propeller including the hub effect. On the other hand, surface panel methods have been remarkably advanced in the field of aerodynamics and hydrodynamics for the design and analysis of three dimensional wings and bodies. The advantages of the panel methods över the lifting surface methods would be to allow more precise representations of a complicated wing body configuration of an aircraft. in the past two decades, the surface panel methods have been applied to the marine propellers including the ducted and the contra rotating propellers and also the advanced turboprop problems. There exist a wide variety of surface panel methods which employ different types of surface panels, singularity distributions, and boundary conditions. Most of the panel methods are based on the Douglas Neumann constant source method developed by Hess and Smith, in which the majör unknovra was the source strength determined from the boundary condition of zero normal velocity at a control point on each panel (Hess and Smith (1966), for lifting bodies, Hess (1972)). Another surface panel formulation has been developed by the application of Green's identity to determine the unknpwn potential strength. A panel method based on Green's identity was first introduced by Morino for general lifting bodies and then, is called Morino method ör Morino formulation. Morino and Kuo (1974). Morino, Chen and Kuo (1975). The Morino method generally produces a well behaved singularity distribution leading to a numerically stable solution and also overcomes some of the problems associated with the Douglas Neumann method on the thin and highly loaded surface. in the Morino method, the governing equations for the velocity potential representing the flow are well known. The velocity potential at any point on the surface of the body can be obtained by a surface integral över the body and wake : xiparabola. The panels are regrouped to form the sets of four neighbouring panels. It is also important to locate their orientation for the two way differentiation of the surface velocity potentials or the dipole potentials. Each panel keeps an array of four neighbouring panels. The derivative along the two directions (for propeller blade radial and circumferential directions) are then found using the expression. *' = 2as + b (4) By choosing the origin of four neighbouring panels at the control point of the centre panel, the derivative is simply found to be equal to the coefficient b of the parabola. From the steady state flow point of view, the shape of the wake is initially not known and the process of finding the proper wake shape (wake roll up) is often denoted as a“slight nonlinearity”in the solution process. In this thesis, two methods for finding the wake shape have been developed. One of them is the hydrodynamic pitch method (HPM), and the other one is the stream line method (SLM). The HPM uses circumferentially averaged axial and tangential velocities. Therefore the hydrodynamic pitch angle of the propeller slipstream (wake) can be obtained for latter iterations as, P = arctan tvA.^ vor - ve (5) where iT. and v8 denote respectively the mean axial and tangential perturbation velocities at a section of the propeller blade. In this method, the radial velocities on the propeller blade are assumed to have no effect on the slipstream and therefore, contractions do not occur in the propeller slipstream along the downstream direction. The SLM uses the stream lines of the propeller blades, hub and their wakes. These stream lines are calculated for each side of the propeller blade, i.e. upper and lower sides. The upper stream line calculation starts at“a sufficient distance”from the trailing edge along its normal direction. This distance can be calculated from the boundary layer thickness obtained from the amprical formulas for a flat plate at the trailing edge and multiplied by a factor obtained from the numerical experiments. A wake strip can be easily calculated after applying the same procedure for the lower streamline and taking the averaged values of upper and lower streamlines. By applying this technique for each radial location on the propeller blade, the new wake shape can be obtained for the latter iterations. The convergence of this method (SLM) is also sufficiently fast, i.e., three or four iterations suffice. Two methods that are mentioned above lead to slightly different results depending on the propeller blade loading. If the blade loading factor introduced by Burril (Kafalı (1983)), tc, is greater than 0.40,the SLM gives satisfactory results. On the other hand, in the case of 0.30 < t. < 0.40, satisfactory results are obtained by the HPM. In the xivA SURFACE PANEL METHOD FOR THE HYDRODYNAMIC ANALYSIS OF HEAVILY LOADED MARINE PROPELLERS SUMMARY in recent years, propellers with various blade geometries such as a highly skewed propeller have been fitted to ships in order to reduce the propeller induced vibration and noise, ör to improve the propulsive perfbrmance of propeller. A reliable numerical method is indispensable for the design and analysis of such propellers. A number of propeller design and analysis methods based on lifting surface theories such as The Vortex Lattice Method (VLM) which could account for the extremely complicated geometries of recent marine propellers, have been developed. However, the propeller lifting surface methods are essentially based on the thin wing theory. Therefore, they are insufficient to predict the pressure distribution on the propeller including the hub effect. On the other hand, surface panel methods have been remarkably advanced in the field of aerodynamics and hydrodynamics for the design and analysis of three dimensional wings and bodies. The advantages of the panel methods över the lifting surface methods would be to allow more precise representations of a complicated wing body configuration of an aircraft. in the past two decades, the surface panel methods have been applied to the marine propellers including the ducted and the contra rotating propellers and also the advanced turboprop problems. There exist a wide variety of surface panel methods which employ different types of surface panels, singularity distributions, and boundary conditions. Most of the panel methods are based on the Douglas Neumann constant source method developed by Hess and Smith, in which the majör unknovra was the source strength determined from the boundary condition of zero normal velocity at a control point on each panel (Hess and Smith (1966), for lifting bodies, Hess (1972)). Another surface panel formulation has been developed by the application of Green's identity to determine the unknpwn potential strength. A panel method based on Green's identity was first introduced by Morino for general lifting bodies and then, is called Morino method ör Morino formulation. Morino and Kuo (1974). Morino, Chen and Kuo (1975). The Morino method generally produces a well behaved singularity distribution leading to a numerically stable solution and also overcomes some of the problems associated with the Douglas Neumann method on the thin and highly loaded surface. in the Morino method, the governing equations for the velocity potential representing the flow are well known. The velocity potential at any point on the surface of the body can be obtained by a surface integral över the body and wake : xi

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