A turbine blade (212, 500), comprising: an airfoil (238, 502) extending outwardly from a root, the airfoil having a trailing edge and a leading edge (242, 504) opposite the trailing edge, the root having a forward side and an aft side; at least one cooling passage (250, 510) defined internally within the turbine blade (212, 500), the at least one cooling passage being in fluid communication with a source of cooling fluid via an inlet (220, 508), the inlet (220, 508) being configured to receive a cooling fluid, the inlet being defined in the forward side of the root, wherein the at least one cooling passage (250, 510) comprises at least a first cooling passage along the leading edge (242, 504), at least one trailing cooling passage, and a second cooling passage between the first cooling passage and the at least one trailing cooling passage, wherein the second cooling passage is a serpentine cooling passage, wherein the first cooling passage is separated from the second cooling passage by a dividing wall defined within the airfoil, the dividing wall separating the first cooling passage from the second cooling passage such that the first cooling passage is not in direct fluid communication with the second cooling passage, wherein the second cooling passage includes a secondary passage inlet that is configured to receive the cooling fluid and the second cooling passage is in fluid communication with one or more trailing conduits downstream from the secondary passage inlet and configured to direct the cooling fluid into the at least one trailing cooling passage; the turbine blade further comprising at least one flow meter defined through the dividing wall of the turbine blade at the inlet (220, 508), the at least one flow meter having a flow meter inlet in fluid communication with the inlet (220, 508) and a flow meter outlet in fluid communication with the secondary passage inlet that is configured to supply the cooling fluid to the second cooling passage, wherein the at least one flow meter is a bore defined through the dividing wall that is configured to supply about 60% to about 100% of the cooling fluid to the second cooling passage; and wherein the second cooling passage is in fluid communication with the first cooling passage at a secondary location, the secondary location defined through the dividing wall and configured to supply about 0% to about 40% of the cooling fluid to the second cooling passage. an airfoil (238, 502) extending outwardly from a root, the airfoil having a trailing edge and a leading edge (242, 504) opposite the trailing edge, the root having a forward side and an aft side; at least one cooling passage (250, 510) defined internally within the turbine blade (212, 500), the at least one cooling passage being in fluid communication with a source of cooling fluid via an inlet (220, 508), the inlet (220, 508) being configured to receive a cooling fluid, the inlet being defined in the forward side of the root, wherein the at least one cooling passage (250, 510) comprises at least a first cooling passage along the leading edge (242, 504), at least one trailing cooling passage, and a second cooling passage between the first cooling passage and the at least one trailing cooling passage, wherein the second cooling passage is a serpentine cooling passage, a first cooling passage along the leading edge (242, 504), at least one trailing cooling passage, and a second cooling passage between the first cooling passage and the at least one trailing cooling passage, wherein the second cooling passage is a serpentine cooling passage, wherein the first cooling passage is separated from the second cooling passage by a dividing wall defined within the airfoil, the dividing wall separating the first cooling passage from the second cooling passage such that the first cooling passage is not in direct fluid communication with the second cooling passage, wherein the second cooling passage includes a secondary passage inlet that is configured to receive the cooling fluid and the second cooling passage is in fluid communication with one or more trailing conduits downstream from the secondary passage inlet and configured to direct the cooling fluid into the at least one trailing cooling passage; the turbine blade further comprising at least one flow meter defined through the dividing wall of the turbine blade at the inlet (220, 508), the at least one flow meter having a flow meter inlet in fluid communication with the inlet (220, 508) and a flow meter outlet in fluid communication with the secondary passage inlet that is configured to supply the cooling fluid to the second cooling passage, wherein the at least one flow meter is a bore defined through the dividing wall that is configured to supply about 60% to about 100% of the cooling fluid to the second cooling passage; and wherein the second cooling passage is in fluid communication with the first cooling passage at a secondary location, the secondary location defined through the dividing wall and configured to supply about 0% to about 40% of the cooling fluid to the second cooling passage.