The interface between rotating and stationary components in a gas turbine is commonly called “disk cavities”. In pursuit of a performance benefit from Secondary Air Flow System (SAF) flow reduction, rotating/stationary disk cavity flow ingestion management in the turbine section becomes an important subject. To completely avoid ingestion, large amount of purging flow is utilized which reduces engine performance. Too much ingestion and the risk of reduced engine durability becomes an issue. Therefore, a partial ingestion condition is desired for optimizing SAF for performance. Typical methodology would be analysing purging flow using 3-D computational fluid dynamics (CFD) modeling in conjunction with engine test data to validate the design and ensure optimal SAF partial ingestion. This approach puts a very heavy demand on computational resources even at steady state. To extend the practice into a transient and unsteady flow field to attempt full design optimization will be even more taxing on computational resources and analysis labor time. An quick alternative would be using a 1-D flow solver for the task in conjunction with baseload main gas path circumferential pressure variation either from main flow path 3D CFD or engine test data. Unfortunately, currently there are no 1-D flow solvers can resolve the poly-directional nature of partial flow ingestion. This paper presents a quick and reliable alternative using a numerical method for augmenting a 1-D flow solver to resolve the partial flow ingestion situation. This is used in conjunction with the 1-D flow solver to resolve the bulk cavity temperature and heat transfer in the disk cavity. The results of this augmented 1-D flow solver show excellent agreement to field measurement data and 3-D CFD solutions. The tool enables a very realistic transient thermal analysis with partial flow ingestion at a fraction of the cost and analysis time of a full 3-D CFD analysis. This enables a faster design optimization with multiple iteration of a turbomachinery disk cavity with partial flow ingestion.