An important aspect concerning the improvement of durability, environmental compatibility and general operating performance of gas turbine combustion chambers is the correct representation of the unsteady processes inside the chamber and the thermal load of combustor walls, i.e. the wall temperature development. Due to geometrical complexity and associated difficulties (from the computational point of view) and the demand for low computational costs the so-called RANS (Reynolds-averaged Navier-Stokes) methods are mostly in use for industrial flow calculations. These methods describe well the general character of the flow, however, due to the time averaging, the unsteady effects are captured insufficiently or not at all. This fact represents an important weakness when dealing with the flow configurations dominated by the large scale unsteadiness, as encountered e.g. in the separating and reattaching flows. The large-eddy simulation (LES) method, by which the large turbulence eddies are resolved directly and the influence of the small eddies is modelled, is regarded as a suitable remedy for the above-mentioned weaknesses. This method is capable to capture the largest portion of the energy containing eddies being most responsible for the turbulent energy transport. However, the price for this are multiply increased computational costs, which are mainly determined by the fact, that the near-wall region has to be appropriately fine resolved. At this point the hybrid LES/RANS method, whose development was the main objective of the present work, comes into play. The goal is to combine the advantages of LES and RANS in order to provide a method which is capable to capture most of the low range (mean flow) and high range (turbulent fluctuations) frequencies in a turbulent flow but at affordable costs. The hybrid formulation proposed enables combinations of any LES, i.e. Subgrid-stress model in the outer layer (flow core) with different, eddy-viscosity based RANS models employed in the wall region. In the present work both the zero equation model due to Smagorinsky (1963) and its dynamic variant (due to Germano et al., 1991) as well as the one-equation model of Yoshizawa (1985) are applied. In the RANS subregion different two-equation models (e.g., Chien model and Launder-Sharma model) and a model based on the homogeneous dissipation concept k-eps_h$ (Jakirlic and Hanjalic, 2002) are used. The most-advanced turbulence model used in this work is the four equation k-eps-zeta-f model, based on the elliptic-relaxation concept (Hanjalic et al., 2004). Key question in a hybrid LES/RANS model scheme is concerned with the coupling of both methods, the inherently steady RANS method and highly-unsteady LES method, along the interface separating two subregions. In the present work large attention was payed to this problem and following three issues were highlighted. First, an indirect, i.e. an implicit exchange of the depending variables between the LES and RANS subregions was proposed, which in a simple but effective manner enables a smooth transition from the RANS to the LES flow region. Second issue addresses the usage of a special forcing technique, which compensates the loss of information due to strong damping in the RANS region by creation of artificial and correlated fluctuations. Hereby, in line with the first issue great importance is attached to simplicity, efficiency and applicability to complex geometries. The third important point is the utilization of an in-the-course-of-the-simulation self-adjusting interface. For the appropriate interface positioning several options reflecting different control parameters are provided within the computational program. The model validation is conducted interactively by computing numerous test cases of different geometrical complexity featuring different mean flow and turbulence phenomena with relevance to the swirl combustor configurations, including low and high Reynolds number cases, isothermal and temperature dependant cases as well as the flows with constant and variable fluid properties. The results obtained with the newly proposed hybrid LES/RANS method exhibit very good agreement with the available reference (experimental, DNS and highly-resolved LES) database. The employment of the present hybrid model enables a substantial reduction of the number of grid points compared to conventional LES method. Concerning spatial and temporal resolution a coarsening by a factor of 4 to 8 and 2 to 4 respectively is shown to be possible by the results quality being comparable to the LES method. It is particularly valid for the integral and wall-related characteristics, which, at marginal increase of the costs (among others, more equations are solved in the hybrid framework), show a considerable improvement compared to the LES on the same grid. Finally, the results obtained by applying the present hybrid model to the flow and mixing in two industrially relevant combustor geometries (tubo-annular combustor and single-annular combustor) including the entire inlet section with swirl generator could confirm its high predictive capability.