Determination of influence of roll angle on drag force of sail-boat class Optimist hull

U natjecateljskom jedrenju, velik utjecaj na brzinu polovidbe ima sila otpora broda. Posebno zahtjevna okolnost po natjecatelje u klasi Optimist i njihovih trenera je i ta da ukupni otpor broda ovisi o više parametara plovidbe. U ovom radu istražen je utjecaj bočnog nagiba na silu otpora trupa jedrilice klase Optimist. Promatrana je ovisnost hidrodinamičkih sila u ovisnosi o kutu bočnog nagiba jedrilice. Sama geometrija jedrilice modelirana je u programskom paketu SolidWorks. Proračunska domena te istisnina jedrilice izrađena je u programskom paketu Salome i to za masu jedrilice od 35kg te srednju masu jedriličara od 45kg. Mreža domene ispunjena je konačnim volumenima generiranim u programskom paketu cf-Mesh. Mrežom dominiraju pravilni heksaedarski volumeni, uz korištenje manjeg broja prijelaznih tetraedarskih i piramidnihćelija te trokutnih prizmi kako bi se sačuvala geometrijska definicija rubova. Svi proračuni provedeni su s ulaznom neporemećenom brzinom od 3 čvora odn. 1.5 m/s. Simulacije su napravljene uz pomoć programskog paketa OpenFoam, koristeći program za rješavanje modela stacionarnog strujanja uz k-omega SST model turbulencije. Za pojednostavljenje proračuna zanemaren je utjecaj valova a rubni uvjet simetrije definiran je na mjestu slobodne površine. Izradeno je ukupno šest simulacija uz promjenu bočnog nagiba jedrilice. U analizi rezultata prikazan je utjecaj tlačnih i viskoznih hidrodinamičkih sila obzirom na kut nagiba jedrilice. Po završetku analize dan je zaključak o tome kako tijelo jedrilice i kut nagiba utječu na ukupnu hidrodinamičku silu koja djeluje na jedrilicu klase Optimist.In competition sailing, drag force of the sailboat has a great impact on sailing speed. Particularly difficult circumstance for competitors in Optimist class and their trainers is that the total drag of the sailboat depends on multiple sail parameters. In this impact of lateral tilt on drag force of the hull class is studied. The dependancy of hydrodynamic force on laterall tilt angle of the sailboat is presented. The sailboat geometry model has been designed in Solidworks program package. Immersed sailboat volume and the corresponding geometrical model of the computational domain is created in Salome software package, for the sailboat mass of 35 kg with average mass of the competitor of 45 kg. Domain grid is filled with finite volume generated in cf-Mesh program package. Mesh is structured by using hexahedron cells, with small number of transitional tetrahedral and pyramidal cells and triangular prisms used to preserve the surfaces of the geometry model. All calculations were performed with the same freerstream velocity of 3 kts (1.5 m/s). For all simulations a steady-state flow model with the k omega SST turbulence model was used as implemented in the OpenFOAM software library. In order to simplify the computational model, wave phenomena are neglected trough applying a symmetry condition at the water free surface. A total of 6 simulations is performed each distinct by the amount of lateral tilt angle of the sailboat. By analyzing the results, the influence of the sailboat tilt angle on resulting pressure and viscous forces is sought. Final results are showing the dependancy of tilt angle on resulting hydrodinamic forces that affect the class Optimist sailboat