In　gas　turbine　engines,　the　first-stage　vanes　usually　suffer　harsh　incoming　flow　conditions　from　the　combustor　with　high　pressure,　high　temperature　and　high　turbulence.　The　combustor-generated　high　freestream　turbulence　and　strong　secondary　flows　in　a　gas　turbine　vane　passage　have　been　reported　to　augment　the　endwall　thermal　load　significantly.　This　paper　presents　a　detailed　numerical　study　on　the　effects　of　high　freestream　turbulence　intensity,　turbulence　length　scale,　and　exit　Reynolds　number　on　the　endwall　secondary　flow　pattern　and　heat　transfer　distribution　of　a　transonic　linear　turbine　vane　passage　at　realistic　engine　Mach　numbers,　with　a　flat　endwall　no　cooling.　Numerical　simulations　were　conducted　at　a　range　of　different　operation　conditions:　six　freestream　turbulence　intensities　(Tu　=　1%,　5%,　10%,　13%,　16%　and　20%),　six　turbulence　length　scales　(normalized　by　the　vane　pitch　of　Λ/P　=　0.01,　0.04,　0.07,　0.12,　0.24,　0.36),　and　three　exit　isentropic　Mach　number　(Maex　=　0.6,　0.85　and　1.02　corresponding　exit　Reynolds　number　Reex　=　1.1×106,　1.7×106　and　2.2×106,　respectively,　based　on　the　vane　chord).　Detailed　comparisons　were　presented　for　endwall　heat　transfer　coefficient　distribution,　endwall　secondary　flow　field　at　different　operation　conditions,　while　paying　special　attention　to　the　link　between　endwall　thermal　load　patterns　and　the　secondary　flow　structures.　Results　show　that　the　freestream　turbulence　intensity　and　length　scale　have　a　significant　influence　on　the　endwall　secondary　flow　field,　but　the　influence　of　the　exit　Reynolds　number　is　very　weak.　The　Nusselt　number　patterns　for　the　higher　turbulence　intensities　(Tu　=　16%,　20%)　appear　to　be　less　affected　by　the　endwall　secondary　flows　than　the　lower　turbulence　cases.　The　thermal　load　distribution　in　the　arc　region　around　the　vane　leading　edge　and　the　banded　region　along　the　vane　pressure　side　are　influenced　most　strongly　by　the　freestream　turbulence　intensity.　In　general,　the　higher　freestream　turbulence　intensities　make　the　vane　endwall　thermal　load　more　uniform.　The　Nusselt　number　distribution　is　only　weakly　affected　by　the　turbulence　length　scale　when　Λ/P　is　larger　than　0.04.　The　heat　transfer　level　appears　to　have　a　significant　uniform　augmentation　over　the　whole　endwall　region　with　the　increasing　Maex.　The　endwall　thermal　load　distribution　is　classified　into　four　typical　regions,　and　the　effects　of　freestream　turbulence,　exit　Reynolds　number　in　each　region　were　discussed　in　detail.　Copyright　©　2020　ASME.